WEXITSTATUS

WEXITSTATUS is a macro used in POSIX-compliant systems to obtain the exit status of a child process from the status value returned by wait or waitpid. It is defined in the header sys/wait.h and is used in conjunction with other wait-related macros such as WIFEXITED and WIFSIGNALED.

Usage and behavior

After a call to wait or waitpid, you receive an int status. You should first check whether the child terminated normally by using WIFEXITED(status). If this returns true, the exit status can be retrieved with WEXITSTATUS(status). The value returned by WEXITSTATUS is an integer in the range 0 to 255, representing the argument passed to exit or _exit by the child process. WEXITSTATUS is only meaningful if WIFEXITED(status) is true; using it otherwise yields an unspecified result.

The status value can also indicate other termination reasons, such as termination by a signal. In that case, WIFSIGNALED(status) would be true and information about the terminating signal can be obtained with WTERMSIG(status). Other macros, such as WIFSTOPPED and WSTOPSIG, provide additional information on stopped processes.

Portability and notes

WEXITSTATUS, along with WIFEXITED and related macros, are part of the POSIX wait macros and are available on systems that provide the POSIX wait interfaces. Include sys/wait.h to access them. While the exact internal encoding of the status value is implementation-defined, the macros abstract away the details, offering a portable way to interpret child termination outcomes.

Example

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

pid_t pid = fork();

if (pid == 0) { _exit(2); }

int status;

waitpid(pid, &status, 0);

if (WIFEXITED(status)) {

int code = WEXITSTATUS(status); // code == 2

}