RPM(8) Red Hat Linux RPM(8)

NAME rpm - RPM Package Manager

SYNOPSIS QUERYING AND VERIFYING PACKAGES: rpm {-q|--query} [select-options] [query-options]

rpm {-V|--verify} [select-options] [verify-options]

rpm --import PUBKEY ...

rpm {-K|--checksig} [--nosignature] [--nodigest] PACKAGE_FILE ...

INSTALLING, UPGRADING, AND REMOVING PACKAGES: rpm {-i|--install} [install-options] PACKAGE_FILE ...

rpm {-U|--upgrade} [install-options] PACKAGE_FILE ...

rpm {-F|--freshen} [install-options] PACKAGE_FILE ...

rpm {-e|--erase} [--allmatches] [--nodeps] [--noscripts] [--notriggers] [--repackage] [--test] PACKAGE_NAME ...

MISCELLANEOUS: rpm {--initdb|--rebuilddb}

rpm {--addsign|--resign} PACKAGE_FILE ...

rpm {--querytags|--showrc}

rpm {--setperms|--setugids} PACKAGE_NAME ...

select-options [PACKAGE_NAME] [-a,--all] [-f,--file FILE] [-g,--group GROUP] {-p,--package PACKAGE_FILE] [--fileid MD5] [--hdrid SHA1] [--pkgid MD5] [--tid TID] [--querybynumber HDRNUM] [--triggeredby PACKAGE_NAME] [--whatprovides CAPABILITY] [--whatrequires CAPABILITY]

query-options [--changelog] [-c,--configfiles] [-d,--docfiles] [--dump] [--filesbypkg] [-i,--info] [--last] [-l,--list] [--provides] [--qf,--queryformat QUERYFMT] [-R,--requires] [--scripts] [-s,--state] [--triggers,--triggerscripts]

verify-options [--nodeps] [--nofiles] [--noscripts] [--nodigest] [--nosignature] [--nolinkto] [--nomd5] [--nosize] [--nouser] [--nogroup] [--nomtime] [--nomode] [--nordev]

install-options [--aid] [--allfiles] [--badreloc] [--excludepath OLDPATH] [--excludedocs] [--force] [-h,--hash] [--ignoresize] [--ignorearch] [--ignoreos] [--includedocs] [--justdb] [--nodeps] [--nodigest] [--nosignature] [--nosuggest] [--noorder] [--noscripts] [--notriggers] [--oldpackage] [--percent] [--prefix NEWPATH] [--relocate OLDPATH=NEWPATH] [--repackage] [--replacefiles] [--replacepkgs] [--test]

DESCRIPTION rpm is a powerful Package Manager, which can be used to build, install, query, verify, update, and erase individual software packages. A pack- age consists of an archive of files and meta-data used to install and erase the archive files. The meta-data includes helper scripts, file attributes, and descriptive information about the package. Packages come in two varieties: binary packages, used to encapsulate software to be installed, and source packages, containing the source code and recipe necessary to produce binary packages.

One of the following basic modes must be selected: Query, Verify, Sig- nature Check, Install/Upgrade/Freshen, Uninstall, Initialize Database, Rebuild Database, Resign, Add Signature, Set Owners/Groups, Show Query- tags, and Show Configuration.

GENERAL OPTIONS These options can be used in all the different modes.

-?, --help Print a longer usage message then normal.

--version Print a single line containing the version number of rpm being used.

--quiet Print as little as possible - normally only error messages will be displayed.

-v Print verbose information - normally routine progress messages will be displayed.

-vv Print lots of ugly debugging information.

--rcfile FILELIST Each of the files in the colon separated FILELIST is read sequentially by rpm for configuration information. Only the first file in the list must exist, and tildes will be expanded to the value of $HOME. The default FILELIST is /usr/lib/rpm/rpmrc:/usr/lib/rpm/red- hat/rpmrc:/etc/rpmrc:~/.rpmrc.

--pipe CMD Pipes the output of rpm to the command CMD.

--dbpath DIRECTORY Use the database in DIRECTORY rather than the default path /var/lib/rpm

--root DIRECTORY Use the file system tree rooted at DIRECTORY for all operations. Note that this means the database within DIRECTORY will be used for dependency checks and any scriptlet(s) (e.g. %post if installing, or %prep if building, a package) will be run after a chroot(2) to DIRECTORY.

-D, --defineMACRO EXPR Defines MACRO with value EXPR.

-E, --evalEXPR Prints macro expansion of EXPR.

INSTALL AND UPGRADE OPTIONS The general form of an rpm install command is

rpm {-i|--install} [install-options] PACKAGE_FILE ...

This installs a new package.

The general form of an rpm upgrade command is

rpm {-U|--upgrade} [install-options] PACKAGE_FILE ...

This upgrades or installs the package currently installed to a newer version. This is the same as install, except all other version(s) of the package are removed after the new package is installed.

rpm {-F|--freshen} [install-options] PACKAGE_FILE ...

This will upgrade packages, but only if an earlier version currently exists. The PACKAGE_FILE may be specified as an ftp or http URL, in which case the package will be downloaded before being installed. See FTP/HTTP OPTIONS for information on rpms internal ftp and http client support.

--aid Add suggested packages to the transaction set when needed.

--allfiles Installs or upgrades all the missingok files in the package, regardless if they exist.

--badreloc Used with --relocate, permit relocations on all file paths, not just those OLDPATHs included in the binary package relocation hint(s).

--excludepath OLDPATH Dont install files whose name begins with OLDPATH.

--excludedocs Don t install any files which are marked as documentation (which includes man pages and texinfo documents).

--force Same as using --replacepkgs, --replacefiles, and --oldpackage.

-h, --hash Print 50 hash marks as the package archive is unpacked. Use with -v|--verbose for a nicer display.

--ignoresize Dont check mount file systems for sufficient disk space before installing this package.

--ignorearch Allow installation or upgrading even if the architectures of the binary package and host dont match.

--ignoreos Allow installation or upgrading even if the operating systems of the binary package and host dont match.

--includedocs Install documentation files. This is the default behavior.

--justdb Update only the database, not the filesystem.

--nodigest Dont verify package or header digests when reading.

--nosignature Don t verify package or header signatures when reading.

--nodeps Dont do a dependency check before installing or upgrading a package.

--nosuggest Don t suggest package(s) that provide a missing dependency.

--noorder Dont reorder the packages for an install. The list of packages would normally be reordered to satisfy dependencies.





--nopostun Dont execute the scriptlet of the same name. The --noscripts option is equivalent to

--nopre --nopost --nopreun --nopostun

and turns off the execution of the corresponding %pre, %post, %preun, and %postun scriptlet(s).




--notriggerpostun Dont execute any trigger scriptlet of the named type. The --notriggers option is equivalent to

--notriggerin --notriggerun --notriggerpostun

and turns off execution of the corresponding %triggerin, %trig- gerun, and %triggerpostun scriptlet(s).

--oldpackage Allow an upgrade to replace a newer package with an older one.

--percent Print percentages as files are unpacked from the package archive. This is intended to make rpm easy to run from other tools.

--prefix NEWPATH For relocatable binary packages, translate all file paths that start with the installation prefix in the package relocation hint(s) to NEWPATH.

--relocate OLDPATH=NEWPATH For relocatable binary packages, translate all file paths that start with OLDPATH in the package relocation hint(s) to NEWPATH. This option can be used repeatedly if several OLDPATHs in the package are to be relocated.

--repackage Re-package the files before erasing. The previously installed package will be named according to the macro %_repack- age_name_fmt and will be created in the directory named by the macro %_repackage_dir (default value is /var/spool/repackage).

--replacefiles Install the packages even if they replace files from other, already installed, packages.

--replacepkgs Install the packages even if some of them are already installed on this system.

--test Do not install the package, simply check for and report poten- tial conflicts.

ERASE OPTIONS The general form of an rpm erase command is

rpm {-e|--erase} [--allmatches] [--nodeps] [--noscripts] [--notriggers] [--repackage] [--test] PACKAGE_NAME ...

The following options may also be used:

--allmatches Remove all versions of the package which match PACKAGE_NAME. Normally an error is issued if PACKAGE_NAME matches multiple packages.

--nodeps Dont check dependencies before uninstalling the packages.



--nopostun Don t execute the scriptlet of the same name. The --noscripts option during package erase is equivalent to

--nopreun --nopostun

and turns off the execution of the corresponding %preun, and %postun scriptlet(s).



--notriggerpostun Don t execute any trigger scriptlet of the named type. The --notriggers option is equivalent to

--notriggerun --notriggerpostun

and turns off execution of the corresponding %triggerun, and %triggerpostun scriptlet(s).

--repackage Re-package the files before erasing. The previously installed package will be named according to the macro %_repack- age_name_fmt and will be created in the directory named by the macro %_repackage_dir (default value is /var/spool/repackage).

--test Dont really uninstall anything, just go through the motions. Useful in conjunction with the -vv option for debugging.

QUERY OPTIONS The general form of an rpm query command is

rpm {-q|--query} [select-options] [query-options]

You may specify the format that package information should be printed in. To do this, you use the

--qf|--queryformat QUERYFMT

option, followed by the QUERYFMT format string. Query formats are mod- ified versions of the standard printf(3) formatting. The format is made up of static strings (which may include standard C character escapes for newlines, tabs, and other special characters) and printf(3) type formatters. As rpm already knows the type to print, the type specifier must be omitted however, and replaced by the name of the header tag to be printed, enclosed by {} characters. Tag names are case insensitive, and the leading RPMTAG_ portion of the tag name may be omitted as well.

Alternate output formats may be requested by following the tag with :typetag. Currently, the following types are supported:

:armor Wrap a public key in ASCII armor.

:base64 Encode binary data using base64.

:date Use strftime(3) "%c" format.

:day Use strftime(3) "%a %b %d %Y" format.

:depflags Format dependency flags.

:fflags Format file flags.

:hex Format in hexadecimal.

:octal Format in octal.

:perms Format file permissions.

:shescape Escape single quotes for use in a script.

:triggertype Display trigger suffix.

For example, to print only the names of the packages queried, you could use %{NAME} as the format string. To print the packages name and dis- tribution information in two columns, you could use %-30{NAME}%{DISTRI- BUTION}. rpm will print a list of all of the tags it knows about when it is invoked with the --querytags argument.

There are two subsets of options for querying: package selection, and information selection.


-a, --all Query all installed packages.

-f, --file FILE Query package owning FILE.

--fileid MD5 Query package that contains a given file identifier, i.e. the MD5 digest of the file contents.

-g, --group GROUP Query packages with the group of GROUP.

--hdrid SHA1 Query package that contains a given header identifier, i.e. the SHA1 digest of the immutable header region.

-p, --package PACKAGE_FILE Query an (uninstalled) package PACKAGE_FILE. The PACKAGE_FILE may be specified as an ftp or http style URL, in which case the package header will be downloaded and queried. See FTP/HTTP OPTIONS for information on rpms internal ftp and http client support. The PACKAGE_FILE argument(s), if not a binary package, will be interpreted as an ASCII package manifest. Comments are permitted, starting with a #, and each line of a package mani- fest file may include white space separated glob expressions, including URLs with remote glob expressions, that will be expanded to paths that are substituted in place of the package manifest as additional PACKAGE_FILE arguments to the query.

--pkgid MD5 Query package that contains a given package identifier, i.e. the MD5 digest of the combined header and payload contents.

--querybynumber HDRNUM Query the HDRNUMth database entry directly; this is useful only for debugging.

--specfile SPECFILE Parse and query SPECFILE as if it were a package. Although not all the information (e.g. file lists) is available, this type of query permits rpm to be used to extract information from spec files without having to write a specfile parser.

--tid TID Query package(s) that have a given TID transaction identifier. A unix time stamp is currently used as a transaction identifier. All package(s) installed or erased within a single transaction have a common identifier.

--triggeredby PACKAGE_NAME Query packages that are triggered by package(s) PACKAGE_NAME.

--whatprovides CAPABILITY Query all packages that provide the CAPABILITY capability.

--whatrequires CAPABILITY Query all packages that requires CAPABILITY for proper function- ing.

PACKAGE QUERY OPTIONS: --changelog Display change information for the package.

-c, --configfiles List only configuration files (implies -l).

-d, --docfiles List only documentation files (implies -l).

--dump Dump file information as follows (implies -l):

path size mtime md5sum mode owner group isconfig isdoc rdev symlink

--filesbypkg List all the files in each selected package.

-i, --info Display package information, including name, version, and description. This uses the --queryformat if one was specified.

--last Orders the package listing by install time such that the latest packages are at the top.

-l, --list List files in package.

--provides List capabilities this package provides.

-R, --requires List packages on which this package depends.

--scripts List the package specific scriptlet(s) that are used as part of the installation and uninstallation processes.

-s, --state Display the states of files in the package (implies -l). The state of each file is one of normal, not installed, or replaced.

--triggers, --triggerscripts Display the trigger scripts, if any, which are contained in the package.

VERIFY OPTIONS The general form of an rpm verify command is

rpm {-V|--verify} [select-options] [verify-options]

Verifying a package compares information about the installed files in the package with information about the files taken from the package metadata stored in the rpm database. Among other things, verifying compares the size, MD5 sum, permissions, type, owner and group of each file. Any discrepancies are displayed. Files that were not installed from the package, for example, documentation files excluded on instal- lation using the "--excludedocs" option, will be silently ignored.

The package selection options are the same as for package querying (including package manifest files as arguments). Other options unique to verify mode are:

--nodeps Dont verify dependencies of packages.

--nodigest Dont verify package or header digests when reading.

--nofiles Dont verify any attributes of package files.

--noscripts Don t execute the %verifyscript scriptlet (if any).

--nosignature Dont verify package or header signatures when reading.








--nordev Dont verify the corresponding file attribute.

The format of the output is a string of 8 characters, a possible attribute marker:

c %config configuration file. d %doc documentation file. g %ghost file (i.e. the file contents are not included in the package payload). l %license license file. r %readme readme file.

from the package header, followed by the file name. Each of the 8 characters denotes the result of a comparison of attribute(s) of the file to the value of those attribute(s) recorded in the database. A single "." (period) means the test passed, while a single "?" (question mark) indicates the test could not be performed (e.g. file permissions prevent reading). Otherwise, the (mnemonically emBoldened) character denotes failure of the corresponding --verify test:

S file Size differs M Mode differs (includes permissions and file type) 5 MD5 sum differs D Device major/minor number mismatch L readLink(2) path mismatch U User ownership differs G Group ownership differs T mTime differs

DIGITAL SIGNATURE AND DIGEST VERIFICATION The general forms of rpm digital signature commands are

rpm --import PUBKEY ...

rpm {--checksig} [--nosignature] [--nodigest] PACKAGE_FILE ...

The --checksig option checks all the digests and signatures contained in PACKAGE_FILE to ensure the integrity and origin of the package. Note that signatures are now verified whenever a package is read, and --checksig is useful to verify all of the digests and signatures asso- ciated with a package.

Digital signatures cannot be verified without a public key. An ASCII armored public key can be added to the rpm database using --import. An imported public key is carried in a header, and key ring management is performed exactly like package management. For example, all currently imported public keys can be displayed by:

rpm -qa gpg-pubkey*

Details about a specific public key, when imported, can be displayed by querying. Heres information about the Red Hat GPG/DSA key:

rpm -qi gpg-pubkey-db42a60e

Finally, public keys can be erased after importing just like packages. Heres how to remove the Red Hat GPG/DSA key

rpm -e gpg-pubkey-db42a60e

SIGNING A PACKAGE rpm --addsign|--resign PACKAGE_FILE ...

Both of the --addsign and --resign options generate and insert new sig- natures for each package PACKAGE_FILE given, replacing any existing signatures. There are two options for historical reasons, there is no difference in behavior currently.

USING GPG TO SIGN PACKAGES In order to sign packages using GPG, rpm must be configured to run GPG and be able to find a key ring with the appropriate keys. By default, rpm uses the same conventions as GPG to find key rings, namely the $GNUPGHOME environment variable. If your key rings are not located where GPG expects them to be, you will need to configure the macro %_gpg_path to be the location of the GPG key rings to use.

For compatibility with older versions of GPG, PGP, and rpm, only V3 OpenPGP signature packets should be configured. Either DSA or RSA ver- ification algorithms can be used, but DSA is preferred.

If you want to be able to sign packages you create yourself, you also need to create your own public and secret key pair (see the GPG man- ual). You will also need to configure the rpm macros

%_signature The signature type. Right now only gpg and pgp are supported.

%_gpg_name The name of the "user" whose key you wish to use to sign your packages.

For example, to be able to use GPG to sign packages as the user "John Doe <jdoe@foo.com>" from the key rings located in /etc/rpm/.gpg using the executable /usr/bin/gpg you would include

%_signature gpg %_gpg_path /etc/rpm/.gpg %_gpg_name John Doe <jdoe@foo.com> %_gpgbin /usr/bin/gpg

in a macro configuration file. Use /etc/rpm/macros for per-system con- figuration and ~/.rpmmacros for per-user configuration.

REBUILD DATABASE OPTIONS The general form of an rpm rebuild database command is

rpm {--initdb|--rebuilddb} [-v] [--dbpath DIRECTORY] [--root DIRECTORY]

Use --initdb to create a new database if one doesnt already exist (existing database is not overwritten), use --rebuilddb to rebuild the database indices from the installed package headers.

SHOWRC The command

rpm --showrc

shows the values rpm will use for all of the options are currently set in rpmrc and macros configuration file(s).

FTP/HTTP OPTIONS rpm can act as an FTP and/or HTTP client so that packages can be queried or installed from the internet. Package files for install, upgrade, and query operations may be specified as an ftp or http style URL:


If the :PASSWORD portion is omitted, the password will be prompted for (once per user/hostname pair). If both the user and password are omit- ted, anonymous ftp is used. In all cases, passive (PASV) ftp transfers are performed.

rpm allows the following options to be used with ftp URLs:

--ftpproxy HOST The host HOST will be used as a proxy server for all ftp trans- fers, which allows users to ftp through firewall machines which use proxy systems. This option may also be specified by config- uring the macro %_ftpproxy.

--ftpport PORT The TCP PORT number to use for the ftp connection on the proxy ftp server instead of the default port. This option may also be specified by configuring the macro %_ftpport.

rpm allows the following options to be used with http URLs:

--httpproxy HOST The host HOST will be used as a proxy server for all http trans- fers. This option may also be specified by configuring the macro %_httpproxy.

--httpport PORT The TCP PORT number to use for the http connection on the proxy http server instead of the default port. This option may also be specified by configuring the macro %_httpport.

LEGACY ISSUES Executing rpmbuild The build modes of rpm are now resident in the /usr/bin/rpmbuild exe- cutable. Although legacy compatibility provided by the popt aliases below has been adequate, the compatibility is not perfect; hence build mode compatibility through popt aliases is being removed from rpm. Install the package containing rpmbuild (usually rpm-build) and see rpmbuild(8) for documentation of all the rpm build modes previously documented here in rpm(8).

Add the following lines to /etc/popt if you wish to continue invoking rpmbuild from the rpm command line:

rpm exec --bp rpmb -bp rpm exec --bc rpmb -bc rpm exec --bi rpmb -bi rpm exec --bl rpmb -bl rpm exec --ba rpmb -ba rpm exec --bb rpmb -bb rpm exec --bs rpmb -bs rpm exec --tp rpmb -tp rpm exec --tc rpmb -tc rpm exec --ti rpmb -ti rpm exec --tl rpmb -tl rpm exec --ta rpmb -ta rpm exec --tb rpmb -tb rpm exec --ts rpmb -ts rpm exec --rebuild rpmb --rebuild rpm exec --recompile rpmb --recompile rpm exec --clean rpmb --clean rpm exec --rmsource rpmb --rmsource rpm exec --rmspec rpmb --rmspec rpm exec --target rpmb --target rpm exec --short-circuit rpmb --short-circuit

FILES rpmrc Configuration /usr/lib/rpm/rpmrc /usr/lib/rpm/redhat/rpmrc /etc/rpmrc ~/.rpmrc

Macro Configuration /usr/lib/rpm/macros /usr/lib/rpm/redhat/macros /etc/rpm/macros ~/.rpmmacros

Database /var/lib/rpm/Basenames /var/lib/rpm/Conflictname /var/lib/rpm/Dirnames /var/lib/rpm/Filemd5s /var/lib/rpm/Group /var/lib/rpm/Installtid /var/lib/rpm/Name /var/lib/rpm/Packages /var/lib/rpm/Providename /var/lib/rpm/Provideversion /var/lib/rpm/Pubkeys /var/lib/rpm/Removed /var/lib/rpm/Requirename /var/lib/rpm/Requireversion /var/lib/rpm/Sha1header /var/lib/rpm/Sigmd5 /var/lib/rpm/Triggername

Temporary /var/tmp/rpm*

SEE ALSO popt(3), rpm2cpio(8), rpmbuild(8),

rpm --help - as rpm supports customizing the options via popt aliases its impossible to guarantee that whats described in the manual matches whats available.

http://www.rpm.org/ <URL:http://www.rpm.org/>

AUTHORS Marc Ewing <marc@redhat.com> Jeff Johnson <jbj@redhat.com> Erik Troan <ewt@redhat.com>

Red Hat, Inc. 09 June 2002 RPM(8) bc(1) bc(1)

NAME bc - An arbitrary precision calculator language

SYNTAX bc [ -hlwsqv ] [long-options] [ file ... ]

VERSION This man page documents GNU bc version 1.06.

DESCRIPTION bc is a language that supports arbitrary precision numbers with inter- active execution of statements. There are some similarities in the syntax to the C programming language. A standard math library is available by command line option. If requested, the math library is defined before processing any files. bc starts by processing code from all the files listed on the command line in the order listed. After all files have been processed, bc reads from the standard input. All code is executed as it is read. (If a file contains a command to halt the processor, bc will never read from the standard input.)

This version of bc contains several extensions beyond traditional bc implementations and the POSIX draft standard. Command line options can cause these extensions to print a warning or to be rejected. This doc- ument describes the language accepted by this processor. Extensions will be identified as such.

OPTIONS -h, --help Print the usage and exit.

-i, --interactive Force interactive mode.

-l, --mathlib Define the standard math library.

-w, --warn Give warnings for extensions to POSIX bc.

-s, --standard Process exactly the POSIX bc language.

-q, --quiet Do not print the normal GNU bc welcome.

-v, --version Print the version number and copyright and quit.

NUMBERS The most basic element in bc is the number. Numbers are arbitrary pre- cision numbers. This precision is both in the integer part and the fractional part. All numbers are represented internally in decimal and all computation is done in decimal. (This version truncates results from divide and multiply operations.) There are two attributes of num- bers, the length and the scale. The length is the total number of sig- nificant decimal digits in a number and the scale is the total number of decimal digits after the decimal point. For example: .000001 has a length of 6 and scale of 6. 1935.000 has a length of 7 and a scale of 3.

VARIABLES Numbers are stored in two types of variables, simple variables and arrays. Both simple variables and array variables are named. Names begin with a letter followed by any number of letters, digits and underscores. All letters must be lower case. (Full alpha-numeric names are an extension. In POSIX bc all names are a single lower case letter.) The type of variable is clear by the context because all array variable names will be followed by brackets ([]).

There are four special variables, scale, ibase, obase, and last. scale defines how some operations use digits after the decimal point. The default value of scale is 0. ibase and obase define the conversion base for input and output numbers. The default for both input and output is base 10. last (an extension) is a variable that has the value of the last printed number. These will be discussed in further detail where appropriate. All of these variables may have values assigned to them as well as used in expressions.

COMMENTS Comments in bc start with the characters /* and end with the characters */. Comments may start anywhere and appear as a single space in the input. (This causes comments to delimit other input items. For exam- ple, a comment can not be found in the middle of a variable name.) Comments include any newlines (end of line) between the start and the end of the comment.

To support the use of scripts for bc, a single line comment has been added as an extension. A single line comment starts at a # character and continues to the next end of the line. The end of line character is not part of the comment and is processed normally.

EXPRESSIONS The numbers are manipulated by expressions and statements. Since the language was designed to be interactive, statements and expressions are executed as soon as possible. There is no "main" program. Instead, code is executed as it is encountered. (Functions, discussed in detail later, are defined when encountered.)

A simple expression is just a constant. bc converts constants into internal decimal numbers using the current input base, specified by the variable ibase. (There is an exception in functions.) The legal values of ibase are 2 through 16. Assigning a value outside this range to ibase will result in a value of 2 or 16. Input numbers may contain the characters 0-9 and A-F. (Note: They must be capitals. Lower case let- ters are variable names.) Single digit numbers always have the value of the digit regardless of the value of ibase. (i.e. A = 10.) For multi-digit numbers, bc changes all input digits greater or equal to ibase to the value of ibase-1. This makes the number FFF always be the largest 3 digit number of the input base.

Full expressions are similar to many other high level languages. Since there is only one kind of number, there are no rules for mixing types. Instead, there are rules on the scale of expressions. Every expression has a scale. This is derived from the scale of original numbers, the operation performed and in many cases, the value of the variable scale. Legal values of the variable scale are 0 to the maximum number repre- sentable by a C integer.

In the following descriptions of legal expressions, "expr" refers to a complete expression and "var" refers to a simple or an array variable. A simple variable is just a name and an array variable is specified as name[expr] Unless specifically mentioned the scale of the result is the maximum scale of the expressions involved.

- expr The result is the negation of the expression.

++ var The variable is incremented by one and the new value is the result of the expression.

-- var The variable is decremented by one and the new value is the result of the expression.

var ++ The result of the expression is the value of the variable and then the variable is incremented by one.

var -- The result of the expression is the value of the variable and then the variable is decremented by one.

expr + expr The result of the expression is the sum of the two expressions.

expr - expr The result of the expression is the difference of the two expressions.

expr * expr The result of the expression is the product of the two expres- sions.

expr / expr The result of the expression is the quotient of the two expres- sions. The scale of the result is the value of the variable scale.

expr % expr The result of the expression is the "remainder" and it is com- puted in the following way. To compute a%b, first a/b is com- puted to scale digits. That result is used to compute a-(a/b)*b to the scale of the maximum of scale+scale(b) and scale(a). If scale is set to zero and both expressions are integers this expression is the integer remainder function.

expr ^ expr The result of the expression is the value of the first raised to the second. The second expression must be an integer. (If the second expression is not an integer, a warning is generated and the expression is truncated to get an integer value.) The scale of the result is scale if the exponent is negative. If the exponent is positive the scale of the result is the minimum of the scale of the first expression times the value of the expo- nent and the maximum of scale and the scale of the first expres- sion. (e.g. scale(a^b) = min(scale(a)*b, max( scale, scale(a))).) It should be noted that expr^0 will always return the value of 1.

( expr ) This alters the standard precedence to force the evaluation of the expression.

var = expr The variable is assigned the value of the expression.

var <op>= expr This is equivalent to "var = var <op> expr" with the exception that the "var" part is evaluated only once. This can make a difference if "var" is an array.

Relational expressions are a special kind of expression that always evaluate to 0 or 1, 0 if the relation is false and 1 if the relation is true. These may appear in any legal expression. (POSIX bc requires that relational expressions are used only in if, while, and for state- ments and that only one relational test may be done in them.) The relational operators are

expr1 < expr2 The result is 1 if expr1 is strictly less than expr2.

expr1 <= expr2 The result is 1 if expr1 is less than or equal to expr2.

expr1 > expr2 The result is 1 if expr1 is strictly greater than expr2.

expr1 >= expr2 The result is 1 if expr1 is greater than or equal to expr2.

expr1 == expr2 The result is 1 if expr1 is equal to expr2.

expr1 != expr2 The result is 1 if expr1 is not equal to expr2.

Boolean operations are also legal. (POSIX bc does NOT have boolean operations). The result of all boolean operations are 0 and 1 (for false and true) as in relational expressions. The boolean operators are:

!expr The result is 1 if expr is 0.

expr && expr The result is 1 if both expressions are non-zero.

expr || expr The result is 1 if either expression is non-zero.

The expression precedence is as follows: (lowest to highest) || operator, left associative && operator, left associative ! operator, nonassociative Relational operators, left associative Assignment operator, right associative + and - operators, left associative *, / and % operators, left associative ^ operator, right associative unary - operator, nonassociative ++ and -- operators, nonassociative

This precedence was chosen so that POSIX compliant bc programs will run correctly. This will cause the use of the relational and logical opera- tors to have some unusual behavior when used with assignment expres- sions. Consider the expression: a = 3 < 5

Most C programmers would assume this would assign the result of "3 < 5" (the value 1) to the variable "a". What this does in bc is assign the value 3 to the variable "a" and then compare 3 to 5. It is best to use parenthesis when using relational and logical operators with the assignment operators.

There are a few more special expressions that are provided in bc. These have to do with user defined functions and standard functions. They all appear as "name(parameters)". See the section on functions for user defined functions. The standard functions are:

length ( expression ) The value of the length function is the number of significant digits in the expression.

read ( ) The read function (an extension) will read a number from the standard input, regardless of where the function occurs. Beware, this can cause problems with the mixing of data and pro- gram in the standard input. The best use for this function is in a previously written program that needs input from the user, but never allows program code to be input from the user. The value of the read function is the number read from the standard input using the current value of the variable ibase for the con- version base.

scale ( expression ) The value of the scale function is the number of digits after the decimal point in the expression.

sqrt ( expression ) The value of the sqrt function is the square root of the expres- sion. If the expression is negative, a run time error is gener- ated.

STATEMENTS Statements (as in most algebraic languages) provide the sequencing of expression evaluation. In bc statements are executed "as soon as pos- sible." Execution happens when a newline in encountered and there is one or more complete statements. Due to this immediate execution, new- lines are very important in bc. In fact, both a semicolon and a newline are used as statement separators. An improperly placed newline will cause a syntax error. Because newlines are statement separators, it is possible to hide a newline by using the backslash character. The sequence "<nl>", where <nl> is the newline appears to bc as whitespace instead of a newline. A statement list is a series of statements sepa- rated by semicolons and newlines. The following is a list of bc state- ments and what they do: (Things enclosed in brackets ([]) are optional parts of the statement.)

expression This statement does one of two things. If the expression starts with "<variable> <assignment> ...", it is considered to be an assignment statement. If the expression is not an assignment statement, the expression is evaluated and printed to the out- put. After the number is printed, a newline is printed. For example, "a=1" is an assignment statement and "(a=1)" is an expression that has an embedded assignment. All numbers that are printed are printed in the base specified by the variable obase. The legal values for obase are 2 through BC_BASE_MAX. (See the section LIMITS.) For bases 2 through 16, the usual method of writing numbers is used. For bases greater than 16, bc uses a multi-character digit method of printing the numbers where each higher base digit is printed as a base 10 number. The multi-character digits are separated by spaces. Each digit contains the number of characters required to represent the base ten value of "obase-1". Since numbers are of arbitrary preci- sion, some numbers may not be printable on a single output line. These long numbers will be split across lines using the " the last character on a line. The maximum number of characters printed per line is 70. Due to the interactive nature of bc, printing a number causes the side effect of assigning the printed value to the special variable last. This allows the user to recover the last value printed without having to retype the expression that printed the number. Assigning to last is legal and will overwrite the last printed value with the assigned value. The newly assigned value will remain until the next num- ber is printed or another value is assigned to last. (Some installations may allow the use of a single period (.) which is not part of a number as a short hand notation for for last.)

string The string is printed to the output. Strings start with a dou- ble quote character and contain all characters until the next double quote character. All characters are take literally, including any newline. No newline character is printed after the string.

print list The print statement (an extension) provides another method of output. The "list" is a list of strings and expressions sepa- rated by commas. Each string or expression is printed in the order of the list. No terminating newline is printed. Expressions are evaluated and their value is printed and assigned to the variable last. Strings in the print statement are printed to the output and may contain special characters. Special characters start with the backslash character (. The special characters recognized by bc are "a" (alert or bell), "b" (backspace), "f" (form feed), "n" (newline), "r" (carriage return), "q" (double quote), "t" (tab), and " Any other character following the backslash will be ignored.

{ statement_list } This is the compound statement. It allows multiple statements to be grouped together for execution.

if ( expression ) statement1 [else statement2] The if statement evaluates the expression and executes state- ment1 or statement2 depending on the value of the expression. If the expression is non-zero, statement1 is executed. If statement2 is present and the value of the expression is 0, then statement2 is executed. (The else clause is an extension.)

while ( expression ) statement The while statement will execute the statement while the expres- sion is non-zero. It evaluates the expression before each exe- cution of the statement. Termination of the loop is caused by a zero expression value or the execution of a break statement.

for ( [expression1] ; [expression2] ; [expression3] ) statement The for statement controls repeated execution of the statement. Expression1 is evaluated before the loop. Expression2 is evalu- ated before each execution of the statement. If it is non-zero, the statement is evaluated. If it is zero, the loop is termi- nated. After each execution of the statement, expression3 is evaluated before the reevaluation of expression2. If expres- sion1 or expression3 are missing, nothing is evaluated at the point they would be evaluated. If expression2 is missing, it is the same as substituting the value 1 for expression2. (The optional expressions are an extension. POSIX bc requires all three expressions.) The following is equivalent code for the for statement: expression1; while (expression2) { statement; expression3; }

break This statement causes a forced exit of the most recent enclosing while statement or for statement.

continue The continue statement (an extension) causes the most recent enclosing for statement to start the next iteration.

halt The halt statement (an extension) is an executed statement that causes the bc processor to quit only when it is executed. For example, "if (0 == 1) halt" will not cause bc to terminate because the halt is not executed.

return Return the value 0 from a function. (See the section on func- tions.)

return ( expression ) Return the value of the expression from a function. (See the section on functions.) As an extension, the parenthesis are not required.

PSEUDO STATEMENTS These statements are not statements in the traditional sense. They are not executed statements. Their function is performed at "compile" time.

limits Print the local limits enforced by the local version of bc. This is an extension.

quit When the quit statement is read, the bc processor is terminated, regardless of where the quit statement is found. For example, "if (0 == 1) quit" will cause bc to terminate.

warranty Print a longer warranty notice. This is an extension.

FUNCTIONS Functions provide a method of defining a computation that can be exe- cuted later. Functions in bc always compute a value and return it to the caller. Function definitions are "dynamic" in the sense that a function is undefined until a definition is encountered in the input. That definition is then used until another definition function for the same name is encountered. The new definition then replaces the older definition. A function is defined as follows: define name ( parameters ) { newline auto_list statement_list } A function call is just an expression of the form "name(parameters)".

Parameters are numbers or arrays (an extension). In the function defi- nition, zero or more parameters are defined by listing their names sep- arated by commas. Numbers are only call by value parameters. Arrays are only call by variable. Arrays are specified in the parameter defi- nition by the notation "name[]". In the function call, actual parame- ters are full expressions for number parameters. The same notation is used for passing arrays as for defining array parameters. The named array is passed by variable to the function. Since function defini- tions are dynamic, parameter numbers and types are checked when a func- tion is called. Any mismatch in number or types of parameters will cause a runtime error. A runtime error will also occur for the call to an undefined function.

The auto_list is an optional list of variables that are for "local" use. The syntax of the auto list (if present) is "auto name, ... ;". (The semicolon is optional.) Each name is the name of an auto vari- able. Arrays may be specified by using the same notation as used in parameters. These variables have their values pushed onto a stack at the start of the function. The variables are then initialized to zero and used throughout the execution of the function. At function exit, these variables are popped so that the original value (at the time of the function call) of these variables are restored. The parameters are really auto variables that are initialized to a value provided in the function call. Auto variables are different than traditional local variables because if function A calls function B, B may access function As auto variables by just using the same name, unless function B has called them auto variables. Due to the fact that auto variables and parameters are pushed onto a stack, bc supports recursive functions.

The function body is a list of bc statements. Again, statements are separated by semicolons or newlines. Return statements cause the ter- mination of a function and the return of a value. There are two ver- sions of the return statement. The first form, "return", returns the value 0 to the calling expression. The second form, "return ( expres- sion )", computes the value of the expression and returns that value to the calling expression. There is an implied "return (0)" at the end of every function. This allows a function to terminate and return 0 with- out an explicit return statement.

Functions also change the usage of the variable ibase. All constants in the function body will be converted using the value of ibase at the time of the function call. Changes of ibase will be ignored during the execution of the function except for the standard function read, which will always use the current value of ibase for conversion of numbers.

As an extension, the format of the definition has been slightly relaxed. The standard requires the opening brace be on the same line as the define keyword and all other parts must be on following lines. This version of bc will allow any number of newlines before and after the opening brace of the function. For example, the following defini- tions are legal.

define d (n) { return (2*n); } define d (n) { return (2*n); }

MATH LIBRARY If bc is invoked with the -l option, a math library is preloaded and the default scale is set to 20. The math functions will calculate their results to the scale set at the time of their call. The math library defines the following functions:

s (x) The sine of x, x is in radians.

c (x) The cosine of x, x is in radians.

a (x) The arctangent of x, arctangent returns radians.

l (x) The natural logarithm of x.

e (x) The exponential function of raising e to the value x.

j (n,x) The bessel function of integer order n of x.

EXAMPLES In /bin/sh, the following will assign the value of "pi" to the shell variable pi.

pi=$(echo "scale=10; 4*a(1)" | bc -l)

The following is the definition of the exponential function used in the math library. This function is written in POSIX bc.

scale = 20

/* Uses the fact that e^x = (e^(x/2))^2 When x is small enough, we use the series: e^x = 1 + x + x^2/2! + x^3/3! + ... */

define e(x) { auto a, d, e, f, i, m, v, z

/* Check the sign of x. */ if (x<0) { m = 1 x = -x }

/* Precondition x. */ z = scale; scale = 4 + z + .44*x; while (x > 1) { f += 1; x /= 2; }

/* Initialize the variables. */ v = 1+x a = x d = 1

for (i=2; 1; i++) { e = (a *= x) / (d *= i) if (e == 0) { if (f>0) while (f--) v = v*v; scale = z if (m) return (1/v); return (v/1); } v += e } }

The following is code that uses the extended features of bc to imple- ment a simple program for calculating checkbook balances. This program is best kept in a file so that it can be used many times without having to retype it at every use.

scale=2 print "0heck book program!0 print " Remember, deposits are negative transactions.0 print " Exit by a 0 transaction.0

print "Initial balance? "; bal = read() bal /= 1 print "0 while (1) { "current balance = "; bal "transaction? "; trans = read() if (trans == 0) break; bal -= trans bal /= 1 } quit

The following is the definition of the recursive factorial function.

define f (x) { if (x <= 1) return (1); return (f(x-1) * x); }

READLINE AND LIBEDIT OPTIONS GNU bc can be compiled (via a configure option) to use the GNU readline input editor library or the BSD libedit library. This allows the user to do editing of lines before sending them to bc. It also allows for a history of previous lines typed. When this option is selected, bc has one more special variable. This special variable, history is the num- ber of lines of history retained. For readline, a value of -1 means that an unlimited number of history lines are retained. Setting the value of history to a positive number restricts the number of history lines to the number given. The value of 0 disables the history fea- ture. The default value is 100. For more information, read the user manuals for the GNU readline, history and BSD libedit libraries. One can not enable both readline and libedit at the same time.

DIFFERENCES This version of bc was implemented from the POSIX P1003.2/D11 draft and contains several differences and extensions relative to the draft and traditional implementations. It is not implemented in the traditional way using dc(1). This version is a single process which parses and runs a byte code translation of the program. There is an "undocu- mented" option (-c) that causes the program to output the byte code to the standard output instead of running it. It was mainly used for debugging the parser and preparing the math library.

A major source of differences is extensions, where a feature is extended to add more functionality and additions, where new features are added. The following is the list of differences and extensions.

LANG This version does not conform to the POSIX standard in the pro- cessing of the LANG environment variable and all environment variables starting with LC_.

names Traditional and POSIX bc have single letter names for functions, variables and arrays. They have been extended to be multi-char- acter names that start with a letter and may contain letters, numbers and the underscore character.

Strings Strings are not allowed to contain NUL characters. POSIX says all characters must be included in strings.

last POSIX bc does not have a last variable. Some implementations of bc use the period (.) in a similar way.

comparisons POSIX bc allows comparisons only in the if statement, the while statement, and the second expression of the for statement. Also, only one relational operation is allowed in each of those statements.

if statement, else clause POSIX bc does not have an else clause.

for statement POSIX bc requires all expressions to be present in the for statement.

&&, ||, ! POSIX bc does not have the logical operators.

read function POSIX bc does not have a read function.

print statement POSIX bc does not have a print statement .

continue statement POSIX bc does not have a continue statement.

return statement POSIX bc requires parentheses around the return expression.

array parameters POSIX bc does not (currently) support array parameters in full. The POSIX grammar allows for arrays in function definitions, but does not provide a method to specify an array as an actual parameter. (This is most likely an oversight in the grammar.) Traditional implementations of bc have only call by value array parameters.

function format POSIX bc requires the opening brace on the same line as the define key word and the auto statement on the next line.

=+, =-, =*, =/, =%, =^ POSIX bc does not require these "old style" assignment operators to be defined. This version may allow these "old style" assign- ments. Use the limits statement to see if the installed version supports them. If it does support the "old style" assignment operators, the statement "a =- 1" will decrement a by 1 instead of setting a to the value -1.

spaces in numbers Other implementations of bc allow spaces in numbers. For exam- ple, "x=1 3" would assign the value 13 to the variable x. The same statement would cause a syntax error in this version of bc.

errors and execution This implementation varies from other implementations in terms of what code will be executed when syntax and other errors are found in the program. If a syntax error is found in a function definition, error recovery tries to find the beginning of a statement and continue to parse the function. Once a syntax error is found in the function, the function will not be callable and becomes undefined. Syntax errors in the interac- tive execution code will invalidate the current execution block. The execution block is terminated by an end of line that appears after a complete sequence of statements. For example, a = 1 b = 2 has two execution blocks and { a = 1 b = 2 } has one execution block. Any runtime error will terminate the execu- tion of the current execution block. A runtime warning will not termi- nate the current execution block.

Interrupts During an interactive session, the SIGINT signal (usually gener- ated by the control-C character from the terminal) will cause execution of the current execution block to be interrupted. It will display a "runtime" error indicating which function was interrupted. After all runtime structures have been cleaned up, a message will be printed to notify the user that bc is ready for more input. All previously defined functions remain defined and the value of all non-auto variables are the value at the point of interruption. All auto variables and function parame- ters are removed during the clean up process. During a non- interactive session, the SIGINT signal will terminate the entire run of bc.

LIMITS The following are the limits currently in place for this bc processor. Some of them may have been changed by an installation. Use the limits statement to see the actual values.

BC_BASE_MAX The maximum output base is currently set at 999. The maximum input base is 16.

BC_DIM_MAX This is currently an arbitrary limit of 65535 as distributed. Your installation may be different.

BC_SCALE_MAX The number of digits after the decimal point is limited to INT_MAX digits. Also, the number of digits before the decimal point is limited to INT_MAX digits.

BC_STRING_MAX The limit on the number of characters in a string is INT_MAX characters.

exponent The value of the exponent in the raise operation (^) is limited to LONG_MAX.

variable names The current limit on the number of unique names is 32767 for each of simple variables, arrays and functions.

ENVIRONMENT VARIABLES The following environment variables are processed by bc:

POSIXLY_CORRECT This is the same as the -s option.

BC_ENV_ARGS This is another mechanism to get arguments to bc. The format is the same as the command line arguments. These arguments are processed first, so any files listed in the environent arguments are processed before any command line argument files. This allows the user to set up "standard" options and files to be processed at every invocation of bc. The files in the environ- ment variables would typically contain function definitions for functions the user wants defined every time bc is run.

BC_LINE_LENGTH This should be an integer specifing the number of characters in an output line for numbers. This includes the backslash and new- line characters for long numbers.

DIAGNOSTICS If any file on the command line can not be opened, bc will report that the file is unavailable and terminate. Also, there are compile and run time diagnostics that should be self-explanatory.

BUGS Error recovery is not very good yet.

Email bug reports to bug-bc@gnu.org. Be sure to include the word bc somewhere in the Subject: field.

AUTHOR Philip A. Nelson philnelson@acm.org

ACKNOWLEDGEMENTS The author would like to thank Steve Sommars (Steve.Sommars@att.com) for his extensive help in testing the implementation. Many great sug- gestions were given. This is a much better product due to his involve- ment.

. bc(1)