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kill(2) System Calls Manual kill(2) NAME kill - Sends a signal to a process or to a group of processes SYNOPSIS #include <signal.h> int kill( pid_t process, int signal ); Application developers may want to specify an #include statement for <sys/types.h> before the one for <signal.h> if programs are being de- veloped for multiple platforms. The additional #include statement is not required on DIGITAL UNIX systems or by ISO or X/Open standards, but may be required on other vendors' systems that conform to these stan- dards. STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: kill(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS Specifies the process or group of processes. Specifies the signal. If the signal parameter is a value of 0 (the null signal), error checking is performed but no signal is sent. This can be used to check the va- lidity of the process parameter. DESCRIPTION The kill() function sends the signal specified by the signal parameter to the process or group of processes specified by the process parame- ter. To send a signal to another process, at least one of the following must be true: The real or the saved set-user-ID of the sending process matches the real or effective user ID of the receiving process. The process is trying to send the SIGCONT signal to one of its session's processes. The calling process has superuser privilege. Processes can send signals to themselves. Sending a signal does not imply that the operation is successful. All signal operations must pass the access checks prescribed by each en- forced access control policy on the system. If the process parameter is greater than 0 (zero), the signal specified by the signal parameter is sent to the process that has a process ID equal to the value of the process parameter. If the process parameter is equal to 0 (zero), the signal specified by the signal parameter is sent to all of the processes (other than system processes) whose process group ID is equal to the process group ID of the sender. If the process parameter is equal to -1 and the effective user ID of the sender has root privileges, the signal specified by the signal pa- rameter is sent to all of the processes other than system processes. If the process parameter is negative but not -1, the signal specified by the signal parameter is sent to all of the processes which have a process group ID equal to the absolute value of the process parameter. RETURN VALUES Upon successful completion, the kill() function returns a value of 0 (zero). Otherwise, a value of -1 is returned and errno is set to indi- cate the error. ERRORS The kill() function sets errno to the specified values for the follow- ing conditions: The signal parameter is not a valid signal number. [Digital] The signal parameter is SIGKILL, SIGSTOP, SIGTSTP or SIGCONT and the process parameter is 1 (proc1). No process or process group can be found corresponding to that specified by the process parameter. The real or saved user ID does not match the real or effective user ID of the receiving process, the calling process does not have appropriate privilege, and the process is not sending a SIGCONT signal to one of its session's processes. [Digital] The calling process does not have appro- priate privilege. RELATED INFORMATION Functions: getpid(2), killpg(2), raise(3), setpgid(2), sigaction(2), sigvec(2) Standards: standards(5) delim off kill(2)