perlfunc
Current Perl documentation can be found at
perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
perlfunc - Perl builtin functions
The functions in this section can serve as terms in an expression. They
fall into two major categories: list operators and named unary operators.
These differ in their precedence relationship with a following comma. (See
the precedence table in the perlop manpage.) List operators take more than one argument, while unary operators can never take more than one argument. Thus, a comma terminates the argument of a unary operator, but merely separates the arguments of a list operator.
A unary operator generally provides a scalar context to its argument, while a list operator may provide either scalar and list contexts for its arguments. If it does both, the scalar arguments will be first, and the list argument will follow. (Note that there can ever be only one list argument.) For instance, splice() has three scalar arguments followed by a list.
In the syntax descriptions that follow, list operators that expect a list (and provide list context for the elements of the list) are shown with
LIST as an argument. Such a list may consist of any combination of scalar arguments or list values; the list values will be included in the list as if each individual element were interpolated at that point in the list, forming a longer single-dimensional list value. Elements of the
LIST should be separated by commas.
Any function in the list below may be used either with or without
parentheses around its arguments. (The syntax descriptions omit the
parentheses.) If you use the parentheses, the simple (but occasionally
surprising) rule is this: It LOOKS like a function, therefore it IS a function, and precedence doesn't matter. Otherwise it's a list operator
or unary operator, and precedence does matter. And whitespace between the
function and left parenthesis doesn't count--so you need to be careful
sometimes:
print 1+2+4; # Prints 7.
print(1+2) + 4; # Prints 3.
print (1+2)+4; # Also prints 3!
print +(1+2)+4; # Prints 7.
print ((1+2)+4); # Prints 7.
If you run Perl with the -w switch it can warn you about this. For example, the third line above
produces:
print (...) interpreted as function at - line 1.
Useless use of integer addition in void context at - line 1.
For functions that can be used in either a scalar or list context,
nonabortive failure is generally indicated in a scalar context by returning
the undefined value, and in a list context by returning the null list.
Remember the following important rule: There is no rule that relates the behavior of an expression in list context to its behavior
in scalar context, or vice versa. It might do two totally different things.
Each operator and function decides which sort of value it would be most
appropriate to return in a scalar context. Some operators return the length
of the list that would have been returned in list context. Some operators
return the first value in the list. Some operators return the last value in
the list. Some operators return a count of successful operations. In
general, they do what you want, unless you want consistency.
An named array in scalar context is quite different from what would at
first glance appear to be a list in scalar context. You can't get a list
like (1,2,3) into being in scalar context, because the compiler knows the context at
compile time. It would generate the scalar comma operator there, not the
list construction version of the comma. That means it was never a list to
start with.
In general, functions in Perl that serve as wrappers for system calls of
the same name (like chown(2), fork(2),
closedir(2), etc.) all return true when they succeed and undef otherwise, as is usually mentioned in the descriptions below. This is different from the
C interfaces, which return
-1 on failure. Exceptions to this rule are perlfunc:wait,
perlfunc:waitpid, and perlfunc:syscall. System calls also set the special $!
variable on failure. Other functions do not, except accidentally.
Here are Perl's functions (including things that look like functions, like
some keywords and named operators) arranged by category. Some functions
appear in more than one place.
- Functions for SCALARs or strings
- chomp, chop, chr, crypt, hex, index, lc, lcfirst,
length, oct, ord, pack, q/STRING/, qq/STRING/, reverse,
rindex, sprintf, substr, tr///, uc, ucfirst, y///
- Regular expressions and pattern matching
- m//, pos, quotemeta, s///, split, study, qr//
- Numeric functions
- abs, atan2, cos, exp, hex, int, log, oct, rand,
sin, sqrt, srand
- Functions for real @ARRAYs
- pop, push, shift, splice, unshift
- Functions for list data
- grep, join, map, qw/STRING/, reverse, sort, unpack
- Functions for real %HASHes
- delete, each, exists, keys, values
- Input and output functions
- 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
- Functions for fixed length data or records
- pack, read, syscall(), sysread, syswrite, unpack, vec
- Functions for filehandles, files, or directories
- -X, chdir, chmod, chown, chroot, fcntl, glob,
ioctl, link, lstat, mkdir, open, opendir, readlink,
rename, rmdir, stat, symlink, umask, unlink, utime
- Keywords related to the control flow of your perl program
- caller, continue, die, do, dump, eval, exit,
goto, last, next, redo, return, sub, wantarray
- Keywords related to scoping
- caller, import, local, my, package, use
- Miscellaneous functions
- defined, dump, eval, formline, local, my, reset,
scalar, undef, wantarray
- Functions for processes and process groups
- alarm, exec, fork, getpgrp, getppid, getpriority, kill,
pipe, qx/STRING/, setpgrp, setpriority, sleep, system,
times, wait(), waitpid()
- Keywords related to perl modules
- do, import, no, package, require, use
- Keywords related to classes and object-orientedness
- bless, dbmclose, dbmopen, package, ref, tie, tied,
untie, use
- Low-level socket functions
- accept, bind, connect, getpeername, getsockname,
getsockopt, listen, recv, send, setsockopt, shutdown,
socket, socketpair
- System V interprocess communication functions
- msgctl, msgget, msgrcv, msgsnd, semctl, semget, semop,
shmctl, shmget, shmread, shmwrite
- Fetching user and group info
- endgrent, endhostent, endnetent, endpwent, getgrent,
getgrgid, getgrnam, getlogin, getpwent, getpwnam,
getpwuid, setgrent, setpwent
- Fetching network info
- endprotoent, endservent, gethostbyaddr, gethostbyname,
gethostent, getnetbyaddr, getnetbyname, getnetent,
getprotobyname, getprotobynumber, getprotoent,
getservbyname, getservbyport, getservent, sethostent,
setnetent, setprotoent, setservent
- Time-related functions
- gmtime, localtime, time, times
- Functions new in perl5
- abs, bless, chomp, chr, exists, formline, glob,
import, lc, lcfirst, map, my, no, prototype, qx,
qw, readline, readpipe, ref, sub*, sysopen, tie,
tied, uc, ucfirst, untie, use
-
* sub was a keyword in perl4, but in perl5 it is an operator, which can be used
in expressions.
- Functions obsoleted in perl5
dbmclose, dbmopen
- -X
- run a file test
- abs
- absolute value function
- accept
- accept an incoming socket connect
- alarm
- schedule a SIGALRM
- atan2
- arctangent of Y/X
- bind
- binds an address to a socket
- binmode
- prepare binary files on old systems
- bless
- create an object
- caller
- get context of the current subroutine call
- chdir
- change your current working directory
- chmod
- changes the permissions on a list of files
- chomp
- remove a trailing record separator from a string
- chop
- remove the last character from a string
- chown
- change the owership on a list of files
- chr
- get character this number represents
- chroot
- make directory new root for path lookups
- close
- close file (or pipe or socket) handle
- closedir
- close directory handle
- connect
- connect to a remove socket
- continue
- optional trailing block in a while or foreach
- cos
- cosine function
- crypt
- one-way passwd-style encryption
- dbmclose
- breaks binding on a tied dbm file
- dbmopen
- create binding on a tied dbm file
- defined
- test whether a value, variable, or function is defined
- delete
- deletes a value from a hash
- die
- raise an exception or bail out
- do
- turn a BLOCK into a TERM
- dump
- create an immediate core dump
- each
- retrieve the next key/value pair from a hash
- endgrent
- be done using group file
- endhostent
- be done using hosts file
- endnetent
- be done using networks file
- endprotoent
- be done using protocols file
- endpwent
- be done using passwd file
- endservent
- be done using services file
- eof
- test a filehandle for its end
- eval
- catch exceptions or compile code
- exec
- abandon this program to run another
- exists
- test whether a hash key is present
- exit
- terminate this program
- exp
- raise e to a power
- fcntl
- file control system all
- fileno
- return file descriptor from filehandle
- flock
- lock an entire file with an advisory lock
- fork
- create a new process just like this one
- format
- declare a picture format with use by the write() function
- formline
- internal function used for formats
- getc
- get the next character from the filehandle
- getgrent
- get next group record
- getgrgid
- get group record given group user ID
- getgrnam
- get group record given group name
- gethostbyaddr
- get host record given its address
- gethostbyname
- get host record given name
- gethostent
- get next hosts record
- getlogin
- return who logged in at this tty
- getnetbyaddr
- get network record given its address
- getnetbyname
- get networks record given name
- getnetent
- get next networks record
- getpeername
- find the other hend of a socket connection
- getpgrp
- get process group
- getppid
- get parent process ID
- getpriority
- get current nice value
- getprotobyname
- get protocol record given name
- getprotobynumber
- get protocol record numeric protocol
- getprotoent
- get next protocols record
- getpwent
- get next passwd record
- getpwnam
- get passwd record given user login name
- getpwuid
- get passwd record given user ID
- getservbyname
- get services record given its name
- getservbyport
- get services record given numeric port
- getservent
- get next services record
- getsockname
- retrieve the sockaddr for a given socket
- getsockopt
- get socket options on a given socket
- glob
- expand filenames using wildcards
- gmtime
- convert UNIX time into record or string using Greenwich time
- goto
- create spaghetti code
- grep
- locate elements in a list test true against a given criterion
- hex
- convert a string to a hexadecimal number
- import
- patch a module's namespace into your own
- int
- get the integer portion of a number
- ioctl
- system-dependent device control system call
- join
- join a list into a string using a separator
- keys
- retrieve list of indices from a hash
- kill
- send a signal to a process or process group
- last
- exit a block prematurely
- lc
- return lower-case version of a string
- lcfirst
- return a string with just the next letter in lower case
- length
- return the number of bytes in a string
- link
- create a hard link in the filesytem
- listen
- register your socket as a server
- local
- create a temporary value for a global variable (dynamic scoping)
- localtime
- convert UNIX time into record or string using local time
- log
- retrieve the natural logarithm for a number
- lstat
- stat a symbolic link
- m//
- match a string with a regular expression pattern
- map
- apply a change to a list to get back a new list with the changes
- mkdir
- create a directory
- msgctl
- SysV IPC message control operations
- msgget
- get SysV IPC message queue
- msgrcv
- receive a SysV IPC message from a message queue
- msgsnd
- send a SysV IPC message to a message queue
- my
- declare and assign a local variable (lexical scoping)
- next
- iterate a block prematurely
- no
- unimport some module symbols or semantics at compile time
- oct
- convert a string to an octal number
- open
- open a file, pipe, or descriptor
- opendir
- open a directory
- ord
- find a character's numeric representation
- pack
- convert a list into a binary representation
- package
- declare a separate global namespace
- pipe
- open a pair of connected filehandles
- pop
- remove the last element from an array and return it
- pos
- find or set the offset for the last/next m//g search
- print
- output a list to a filehandle
- printf
- output a formatted list to a filehandle
- prototype
- get the prototype (if any) of a subroutine
- push
- append one or more elements to an array
- q/STRING/
- singly quote a string
- qq/STRING/
- doubly quote a string
- quotemeta
- quote regular expression magic characters
- qw/STRING/
- quote a list of words
- qx/STRING/
- backquote quote a string
- rand
- retrieve the next pseudorandom number
- read
- fixed-length buffered input from a filehandle
- readdir
- get a directory from a directory handle
- readlink
- determine where a symbolic link is pointing
- recv
- receive a message over a Socket
- redo
- start this loop iteration over again
- ref
- find out the type of thing being referenced
- rename
- change a filename
- require
- load in external functions from a library at runtime
- reset
- clear all variables of a given name
- return
- get out of a function early
- reverse
- flip a string or a list
- rewinddir
- reset directory handle
- rindex
- right-to-left substring search
- rmdir
- remove a directory
- s///
- replace a pattern with a string
- scalar
- force a scalar context
- seek
- reposition file pointer for random-access I/O
- seekdir
- reposition directory pointer
- select
- reset default output or do I/O multiplexing
- semctl
- SysV semaphore control operations
- semget
- get set of SysV semaphores
- semop
- SysV semaphore operations
- send
- send a message over a socket
- setgrent
- prepare group file for use
- sethostent
- prepare hosts file for use
- setnetent
- prepare networks file for use
- setpgrp
- set the process group of a process
- setpriority
- set a process's nice value
- setprotoent
- prepare protocols file for use
- setpwent
- prepare passwd file for use
- setservent
- prepare services file for use
- setsockopt
- set some socket options
- shift
- remove the first element of an array, and return it
- shmctl
- SysV shared memory operations
- shmget
- get SysV shared memory segment identifier
- shmread
- read SysV shared memory
- shmwrite
- write SysV shared memory
- shutdown
- close down just half of a socket connection
- sin
- return the sin of a number
- sleep
- block for some number of seconds
- socket
- create a socket
- socketpair
- create a pair of sockets
- sort
- sort a list of values
- splice
- add or remove elements anywhere in an array
- split
- split up a string using a regexp delimiter
- sprintf
- formatted print into a string
- sqrt
- square root function
- srand
- seed the random number generator
- stat
- get a file's status information
- study
- optimize input data for repeated searches
- sub
- declare a subroutine, possibly anonymously
- substr
- get or alter a portion of a stirng
- symlink
- create a symbolic link to a file
- syscall()
- execute an arbitrary system call
- sysread
- fixed-length unbuffered input from a filehandle
- system
- run a separate program
- syswrite
- fixed-length unbuffered output to a filehandle
- tell
- get current seekpointer on a filehandle
- telldir
- get current seekpointer on a directory handle
- tie
- bind a variable to an object class
- time
- return number of seconds since 1970
- times
- return elapsed time for self and child processes
- tr///
- transliterate a string
- truncate
- shorten a file
- uc
- return upper-case version of a string
- ucfirst
- return a string with just the next letter in upper case
- umask
- set file creation mode mask
- undef
- remove a variable or function definition
- unlink
- remove one link to a file
- unpack
- convert binary structure into normal perl variables
- unshift
- prepend more elements to the beginning of a list
- untie
- break a tie binding to a variable
- use
- load in a module at compile time
- utime
- set a file's last access and modify times
- values
- return a list of the values in a hash
- vec
- test or set particular bits in a string
- wait()
- wait for any child process to die
- waitpid()
- wait for a particular child process to die
- wantarray
- get list vs array context of current subroutine call
- warn
- print debugging info
- write
- print a picture record
- y///
- transliterate a string
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