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Does the same as the system call of that name. If you don t know what it does, don t worry about
it. If FILENAME is omitted, does chroot to $_.
die(LIST)
die LIST
Outside of an eval, prints the value of LIST to STDERR and exits with the current value of $!
(errno). If $! is 0, exits with the value of ($? >> 8) (\ command\ status). If ($? >> 8) is 0, exits
with 255. Inside an eval, the error message is stuffed into $@ and the eval is terminated with the
undefined value.
Equivalent examples:
die "Can t cd to spool: $!\n"
unless chdir  /usr/spool/news ;
chdir  /usr/spool/news || die "Can t cd to spool: $!\n"
If the value of EXPR does not end in a newline, the current script line number and input line
number (if any) are also printed, and a newline is supplied. Hint: sometimes appending ", stopped"
to your message will cause it to make better sense when the string "at foo line 123" is appended.
Suppose you are running script "canasta".
die "/etc/games is no good";
die "/etc/games is no good, stopped";
produce, respectively
/etc/games is no good at canasta line 123.
/etc/games is no good, stopped at canasta line 123.
See also exit.
exec(LIST)
exec LIST
If there is more than one argument in LIST, or if LIST is an array with more than one value, calls
execvp() with the arguments in LIST. If there is only one scalar argument, the argument is checked
for shell metacharacters. If there are any, the entire argument is passed to "/bin/sh -c" for parsing.
If there are none, the argument is split into words and passed directly to execvp(), which is more
efficient. Note: exec (and system) do not flush your output buffer, so you may need to set $| to
avoid lost output. Examples:
exec  /bin/echo ,  Your arguments are:  , @ARGV;
exec "sort $outfile | uniq";
If you don t really want to execute the first argument, but want to lie to the program you are
executing about its own name, you can specify the program you actually want to run by assigning
that to a variable and putting the name of the variable in front of the LIST without a comma. (This
always forces interpretation of the LIST as a multi-valued list, even if there is only a single scalar
in the list.) Example:
$shell =  /bin/csh ;
exec $shell  -sh ; # pretend it s a login shell
exit(EXPR)
exit EXPR
Evaluates EXPR and exits immediately with that value. Example:
$ans = ;
exit 0 if $ans =~/^[Xx]/;
See also die. If EXPR is omitted, exits with 0 status.
fork Does a fork() call. Returns the child pid to the parent process and 0 to the child process. Note:
unflushed buffers remain unflushed in both processes, which means you may need to set $| to
avoid duplicate output.
getlogin
Returns the current login from /etc/utmp, if any. If null, use getpwuid. $login = getlogin ||
(getpwuid($
getpgrp(PID)
getpgrp PID
Returns the current process group for the specified PID, 0 for the current process. Will produce a
fatal error if used on a machine that doesn t implement getpgrp(2). If EXPR is omitted, returns
process group of current process.
getppid
Returns the process id of the parent process.
getpriority(WHICH,WHO)
Returns the current priority for a process, a process group, or a user. (See getpriority(2).) Will
produce a fatal error if used on a machine that doesn t implement getpriority(2).
kill(LIST)
kill LIST
Sends a signal to a list of processes. The first element of the list must be the signal to send. Returns
the number of processes successfully signaled.
$cnt = kill 1, $child1, $child2;
kill 9, @goners;
If the signal is negative, kills process groups instead of processes. (On System V, a negative
process number will also kill process groups, but that s not portable.) You may use a signal name
in quotes.
setpgrp(PID,PGRP)
Sets the current process group for the specified PID, 0 for the current process. Will produce a fatal
error if used on a machine that doesn t implement setpgrp(2).
setpriority(WHICH,WHO,PRIORITY)
Sets the current priority for a process, a process group, or a user. (See setpriority(2).) Will produce
a fatal error if used on a machine that doesn t implement setpriority(2).
sleep(EXPR)
sleep EXPR
sleep Causes the script to sleep for EXPR seconds, or forever if no EXPR. May be interrupted by
sending the process a SIGALRM. Returns the number of seconds actually slept. You probably
cannot mix alarm() and sleep() calls, since sleep() is often implemented using alarm().
syscall(LIST)
syscall LIST
Calls the system call specified as the first element of the list, passing the remaining elements as
arguments to the system call. If unimplemented, produces a fatal error. The arguments are [ Pobierz całość w formacie PDF ]