NAME

perlfunc - Perl builtin functions


DESCRIPTION

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 rule:

THERE IS NO GENERAL RULE FOR CONVERTING A LIST INTO A SCALAR!
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 a 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.


Perl Functions by Category

Here are Perl's functions (including things that look like functions, like some of the 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

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 , 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 , ioctl , 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


Alphabetical Listing of Perl Functions

X , abs , accept , alarm , atan2 , bind , binmode , bless , caller , chdir , chmod , chomp , chop , chown , chr , chroot , close , closedir , connect , continue , cos , crypt , dbmclose , dbmopen , defined , delete , die , do , dump , each , endgrent , endhostent , endnetent , endprotoent , endpwent , endservent , eof , eval , exec , exists , exit , exp , fcntl , fileno , flock , fork , format , formline , getc , getgrent , getgrgid , getgrnam , gethostbyaddr , gethostbyname , gethostent , getlogin , getnetbyaddr , getnetbyname , getnetent , getpeername , getpgrp , getppid , getpriority , getprotobyname , getprotobynumber , getprotoent , getpwent , getpwnam , getpwuid , getservbyname , getservbyport , getservent , getsockname , getsockopt , glob , gmtime , goto , grep , hex , import , index , int , ioctl , join , keys , kill , last , lc , lcfirst , length , link , listen , local , localtime , log , lstat , m , map , mkdir , msgctl , msgget , msgrcv , msgsnd , my , next , no , oct , open , opendir , ord , pack , package , pipe , pop , pos , print , printf , prototype , push , qSTRING , qqSTRING , quotemeta , qwSTRING , qxSTRING , rand , read , readdir , readline , readlink , readpipe , recv , redo , ref , rename , require , reset , return , reverse , rewinddir , rindex , rmdir , s , scalar , seek , seekdir , select , semctl , semget , semop , send , setgrent , sethostent , setnetent , setpgrp , setpriority , setprotoent , setpwent , setservent , setsockopt , shift , shmctl , shmget , shmread , shmwrite , shutdown , sin , sleep , socket , socketpair , sort , splice , split , sprintf , sqrt , srand , stat , study , sub , substr , symlink , syscall , sysopen , sysread , sysseek , system , syswrite , tell , telldir , tie , tied , time , times , tr , truncate , uc , ucfirst , umask , undef , unlink , unpack , unshift , untie , use , utime , values , vec , wait , waitpid , wantarray , warn , write , y