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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 perlop.) 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 or 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 such list argument.) For instance, splice() has three scalar arguments followed by a
list, whereas gethostbyname() has four scalar arguments.
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.
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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.
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A few functions take no arguments at all, and therefore work as neither unary nor list
operators. These include such functions as time and endpwent. For
example, time+86_400
always means time() + 86_400.
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 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.
A 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 wait, waitpid, and 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, sysopen, 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, our, package, use
- Miscellaneous functions
defined,
dump, eval, formline, local, my, our, 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, our, 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
Perl was born in Unix and can therefore access all common Unix system calls. In non-Unix
environments, the functionality of some Unix system calls may not be available, or details of
the available functionality may differ slightly. The Perl functions affected by this are:
-X, binmode, chmod, chown, chroot, crypt, dbmclose, dbmopen, dump, endgrent, endhostent, endnetent, endprotoent, endpwent, endservent, exec, fcntl, flock, fork, getgrent, getgrgid, gethostent, getlogin, getnetbyaddr, getnetbyname, getnetent, getppid, getprgp,
getpriority,
getprotobynumber,
getprotoent, getpwent, getpwnam, getpwuid, getservbyport, getservent, getsockopt, glob, ioctl, kill, link, lstat, msgctl, msgget, msgrcv, msgsnd, open, pipe, readlink, rename, select, semctl, semget, semop, setgrent, sethostent, setnetent, setpgrp, setpriority, setprotoent, setpwent, setservent, setsockopt, shmctl, shmget, shmread, shmwrite, socket, socketpair, stat, symlink, syscall, sysopen, system, times, truncate, umask, unlink, utime, wait, waitpid
For more information about the portability of these functions, see perlport and other available
platform-specific documentation.
-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, lock, log, lstat
m, map, mkdir, msgctl, msgget, msgrcv, msgsnd, my
next, no
oct, open, opendir, ord, our
pack, package, pipe, pop, pos, print, printf, prototype, push
q, qq, qr, quotemeta, qw, qx
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
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