5. Function Reference

Contents:
Perl Functions by Category
Perl Functions in Alphabetical Order

This chapter gives a brief description of Perl's built-in functions. Each description gives the syntax of the function, with the types and order of its arguments.

Required arguments are shown in italics, separated by commas. If an argument must be a specific variable type, that variable's identifier will be used (i.e., a percent sign for a hash, %hash). Optional arguments are placed in brackets. Do not actually use the brackets in your function calls unless you really want to use an anonymous hash reference.

There are different ways to use a built-in function. For starters, any argument that requires a scalar value can be made up of any expression that returns one. For example, you can obtain the square root of the first value in an array:

$root = sqrt (shift @numbers);

shift removes the first element of @numbers and returns it to be used by sqrt.

Many functions take a list of scalars for arguments. Any array variable or other expression that returns a list can be used for all or part of the arguments. For example:

chmod (split /,/ FILELIST>); # an expression returns a list
chmod 0755, @executables;    # array used for part of arguments

In the first line, the split expression reads a string from a filehandle and splits it into a list. The list provides proper arguments for chmod. The second line uses an array that contains a list of filenames for chmod to act upon.

Parentheses are not required around a function's arguments. However, without parentheses, functions are viewed as operators in an expression (the same is true of predeclared subroutines). If you use a function in a complex expression, you may want to use parentheses for clarity. See Chapter 4, The Perl Language, for more about precedence in Perl expressions.

5.1 Perl Functions by Category

Here are Perl's functions and function-like keywords, arranged by category. Note that some functions appear under more than one heading.

Scalar manipulation

chomp, chop, chr, crypt, hex, index, lc, lcfirst, length, oct, ord, pack, q//, qq//, reverse, rindex, sprintf, substr, tr///, uc, ucfirst, y///

Regular expressions and pattern matching

m//, pos, qr//, quotemeta, s///, split, study

Numeric functions

abs, atan2, cos, exp, hex, int, log, oct, rand, sin, sqrt, srand

Array processing

pop, push, shift, splice, unshift

List processing

grep, join, map, qw//, reverse, sort, unpack

Hash processing

delete, each, exists, keys, values

Input and output

binmode, close, closedir, dbmclose, dbmopen, die, eof, fileno, flock, format, getc, print, printf, read, readdir, rewinddir, seek, seekdir, select, syscall, sysread, sysseek, syswrite, tell, telldir, truncate, warn, write

Fixed-length data and records

pack, read, syscall, sysread, syswrite, unpack, vec

Filehandles, files, and directories

chdir, chmod, chown, chroot, fcntl, glob, ioctl, link, lstat, mkdir, open, opendir, readlink, rename, rmdir, stat, symlink, sysopen, umask, unlink, utime

Flow of program control

caller, continue, die, do, dump, eval, exit, goto, last, next, redo, return, sub, wantarray

Scoping

caller, import, local, my, package, use

Miscellaneous

defined, dump, eval, formline, local, my, prototype, reset, scalar, undef, wantarray

Processes and process groups

alarm, exec, fork, getpgrp, getppid, getpriority, kill, pipe, qx//, setpgrp, setpriority, sleep, system, times, wait, waitpid

Library modules

do, import, no, package, require, use

Classes and objects

bless, dbmclose, dbmopen, package, ref, tie, tied, untie, use

Low-level socket access

accept, bind, connect, getpeername, getsockname, getsockopt, listen, recv, send, setsockopt, shutdown, socket, socketpair

System V interprocess communication

msgctl, msgget, msgrcv, msgsnd, semctl, semget, semop, shmctl, shmget, shmread, shmwrite

Fetching user and group information

endgrent, endhostent, endnetent, endpwent, getgrent, getgrgid, getgrnam, getlogin, getpwent, getpwnam, getpwuid, setgrent, setpwent

Fetching network information

endprotoent, endservent, gethostbyaddr, gethostbyname, gethostent, getnetbyaddr, getnetbyname, getnetent, getprotobyname, getprotobynumber, getprotoent, getservbyname, getservbyport, getservent, sethostent, setnetent, setprotoent, setservent

Time

gmtime, localtime, time, times