system -- execute a shell command


#include <stdlib.h>

int system(const char * string);


The system() function shall behave as described in POSIX 1003.1-2008 (ISO/IEC 9945-2009).


The fact that system() ignores interrupts is often not what a program wants. POSIX 1003.1-2008 (ISO/IEC 9945-2009) describes some of the consequences; an additional consequence is that a program calling system() from a loop cannot be reliably interrupted. Many programs will want to use the exec() family of functions instead.

Do not use system() from a program with suid or sgid privileges, because unexpected values for some environment variables might be used to subvert system integrity. Use the exec() family of functions instead, but not execlp() or execvp(). system() will not, in fact, work properly from programs with suid or sgid privileges on systems on which /bin/sh is bash version 2, since bash 2 drops privileges on startup. (Debian uses a modified bash which does not do this when invoked as sh.)

The check for the availability of /bin/sh is not actually performed; it is always assumed to be available. ISO C (1999) specifies the check, but POSIX 1003.1-2008 (ISO/IEC 9945-2009) specifies that the return shall always be nonzero, since a system without the shell is not conforming, and it is this that is implemented.

It is possible for the shell command to return 127, so that code is not a sure indication that the execve() call failed; check the global variable errno to make sure.