WEXITSTATUSstatus

WEXITSTATUS is a macro defined in the POSIX standard used to extract the exit status from a status value returned by wait, waitpid, and related functions. It provides access to the argument given to exit() or the value returned from main, as encoded in the child’s termination status.

Usage and semantics: After a successful wait call, a status integer is filled. The WIFEXITED(status) macro can be used to check whether the child terminated normally. If true, WEXITSTATUS(status) yields the low eight bits of the exit status, i.e., the value passed to exit() or returned from main, typically in the range 0–255. If WIFEXITED(status) is false, the result of WEXITSTATUS(status) is not defined and should not be used.

Relation to other macros: WEXITSTATUS is part of a family of macros for decoding process termination information from the same status value. Common companions include WIFSIGNALED(status) with WTERMSIG(status) to determine if a process was terminated by a signal and which signal caused termination, as well as WIFSTOPPED(status) with WSTOPSIG(status) for stopped processes, and WIFCONTINUED(status) for continued processes. Proper usage requires checking the appropriate condition (e.g., WIFEXITED) before calling WEXITSTATUS.

Implementation notes: WEXITSTATUS is typically defined as a macro in <sys/wait.h> and operates on the status value provided by wait or waitpid. The exact representation of the status is implementation-defined, but the macros provide a portable, well-defined interface for interpreting it.