[Chapter 5] Function Reference
Author: Ellen Siever, Stephen Spainhour & Nathan Patwardhan
Date: 1999-07-02T01:33:38Z

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| Chapter 5 |

# 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`

4.11 Pod |  | 5.2 Perl Functions in Alphabetical Order