C figure 829 signal2 an improved version of figure

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Unformatted text preview: signal (number 9). When a child process terminates or stops, the kernel sends a SIGCHLD signal (number 17) to the parent. 420 CHAPTER 8. EXCEPTIONAL CONTROL FLOW code/ecf/shellex.c 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 /* eval - evaluate a command line */ void eval(char *cmdline) { char *argv[MAXARGS]; /* argv for execve() */ int bg; /* should the job run in bg or fg? */ pid_t pid; /* process id */ bg = parseline(cmdline, argv); if (argv[0] == NULL) return; /* ignore empty lines */ if (!builtin_command(argv)) { if ((pid = Fork()) == 0) { /* child runs user job */ if (execve(argv[0], argv, environ) < 0) { printf("%s: Command not found.\n", argv[0]); exit(0); } } /* parent waits for foreground job to terminate */ if (!bg) { int status; if (waitpid(pid, &status, 0) < 0) unix_error("waitfg: waitpid error"); } else printf("%d %s", pid, cmdline); } return; } /* if first arg is a builtin command, run it and return true */ int builtin_co...
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