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# Perl functions A-Z

Perl 5 version 18.2 documentation
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# Perl functions A-Z

Perl functions A-Z | Perl functions by category | The 'perlfunc' manpage
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

## A

- AUTOLOAD
- abs - absolute value function
- accept - accept an incoming socket connect
- alarm - schedule a SIGALRM
- and
- atan2 - arctangent of Y/X in the range -PI to PI

## B

- BEGIN
- bind - binds an address to a socket
- binmode - prepare binary files for I/O
- bless - create an object
- break - break out of a "given" block

## C

- CHECK
- 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
- cmp
- connect - connect to a remote socket
- continue - optional trailing block in a while or foreach
- cos - cosine function
- crypt - one-way passwd-style encryption

## D

- DESTROY
- __DATA__
- dbmclose - breaks binding on a tied dbm file
- dbmopen - create binding on a tied dbm file
- default
- 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

## E

- END
- __END__
- each - retrieve the next key/value pair from a hash
- else
- elseif
- elsif
- 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
- eq
- eval - catch exceptions or compile and run code
- evalbytes
- exec - abandon this program to run another
- exists - test whether a hash key is present
- exit - terminate this program
- exp - raise I<e> to a power

## F

- __FILE__
- fc
- fcntl - file control system call
- fileno - return file descriptor from filehandle
- flock - lock an entire file with an advisory lock
- for
- foreach
- 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

## G

- ge
- 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 end 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
- given
- 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
- gt

## H

- hex - convert a string to a hexadecimal number

## I

- INIT
- if
- import - patch a module's namespace into your own
- index - find a substring within a string
- int - get the integer portion of a number
- ioctl - system-dependent device control system call

## J

- join - join a list into a string using a separator

## K

- keys - retrieve list of indices from a hash
- kill - send a signal to a process or process group

## L

- __LINE__
- 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
- le
- 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
- lock - get a thread lock on a variable, subroutine, or method
- log - retrieve the natural logarithm for a number
- lstat - stat a symbolic link
- lt

## M

- 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)

## N

- ne
- next - iterate a block prematurely
- no - unimport some module symbols or semantics at compile time
- not

## O

- oct - convert a string to an octal number
- open - open a file, pipe, or descriptor
- opendir - open a directory
- or
- ord - find a character's numeric representation
- our - declare and assign a package variable (lexical scoping)

## P

- __PACKAGE__
- 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

- q - singly quote a string
- qq - doubly quote a string
- qr - Compile pattern
- quotemeta - quote regular expression magic characters
- qw - quote a list of words
- qx - backquote quote a string

## R

- rand - retrieve the next pseudorandom number
- read - fixed-length buffered input from a filehandle
- readdir - get a directory from a directory handle
- readline - fetch a record from a file
- readlink - determine where a symbolic link is pointing
- readpipe - execute a system command and collect standard output
- 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

- __SUB__
- s - replace a pattern with a string
- say - print with newline
- 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 sine 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
- state - declare and assign a state variable (persistent lexical scoping)
- 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
- sysopen - open a file, pipe, or descriptor
- sysread - fixed-length unbuffered input from a filehandle
- sysseek - position I/O pointer on handle used with sysread and syswrite
- system - run a separate program
- syswrite - fixed-length unbuffered output to a filehandle

## T

- tell - get current seekpointer on a filehandle
- telldir - get current seekpointer on a directory handle
- tie - bind a variable to an object class
- tied - get a reference to the object underlying a tied variable
- time - return number of seconds since 1970
- times - return elapsed time for self and child processes
- tr - transliterate a string
- truncate - shorten a file

## U

- UNITCHECK
- 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
- unless
- 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
- until
- use - load in a module at compile time
- utime - set a file's last access and modify times

## V

- values - return a list of the values in a hash
- vec - test or set particular bits in a string

## W

- wait - wait for any child process to die
- waitpid - wait for a particular child process to die
- wantarray - get void vs scalar vs list context of current subroutine call
- warn - print debugging info
- when
- while
- write - print a picture record

## X

- -X - a file test (-r, -x, etc)
- x
- xor

## Y

- y - transliterate a string