system —
pass a command to the shell
#include
<stdlib.h>
int
system(
const
char *string);
The
system() function hands the argument
string to the command interpreter
sh(1). The calling
process waits for the shell to finish executing the command, ignoring
SIGINT and
SIGQUIT, and blocking
SIGCHLD.
If
string is
NULL,
system() will return non-zero. Otherwise,
system() returns the termination status of
the shell in the format specified by
waitpid(2).
Note that fork handlers established using
pthread_atfork(3)
are not called when a multithreaded program calls
system().
If a child process cannot be created, or the termination status of the shell
cannot be obtained,
system() returns -1 and
sets
errno to indicate the error. If
execution of the shell fails,
system()
returns the termination status for a program that terminates with a call of
exit(
127).
sh(1),
execve(2),
waitpid(2),
popen(3)
The
system() function conforms to
ANSI X3.159-1989
(“ANSI C89”) and
IEEE
Std 1003.2-1992 (“POSIX.2”).
The
system() function first appeared in
Version 6 AT&T UNIX.
Never supply the
system() function with a
command containing any part of an unsanitized user-supplied string. Shell
meta-characters present will be honored by the
sh(1) command
interpreter.
It is often simpler to bypass the shell and run an external command using
fork(2),
execlp(3), and
waitpid(2) directly
instead of having to sanitize a string for shell consumption.
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