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setpgid, setpgrp — set process group
Standard C Library (libc, -lc)
#include <unistd.h> int setpgid(pid_t pid, pid_t pgrp); int setpgrp(pid_t pid, pid_t pgrp);
The setpgid() system call sets the process group of the specified process pid to the specified pgrp. If pid is zero, then the call applies to the current process. If pgrp is zero, then the process id of the process specified by pid is used instead. If the affected process is not the invoking process, then it must be a child of the invoking process, it must not have performed an exec(3) operation, and both processes must be in the same session. The requested process group ID must already exist in the session of the caller, or it must be equal to the target process ID.
The setpgid() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
The setpgrp() system call is identical to setpgid(), and is retained for calling convention compatibility with historical versions of BSD.
The setpgid() system call will fail and the process group will not be altered if: [EINVAL] The requested process group ID is not legal. [ESRCH] The requested process does not exist. [ESRCH] The target process is not the calling process or a child of the calling process. [EACCES] The requested process is a child of the calling process, but it has performed an exec(3) operation. [EPERM] The target process is a session leader. [EPERM] The requested process group ID is not in the session of the caller, and it is not equal to the process ID of the target process.
The setpgid() system call is expected to conform to ISO/IEC 9945-1:1990 (“POSIX.1”).