UNIX — универсальная среда программирования - Керниган Брайан Уилсон
#include "error.c"
3.8.52 system1.c
#include <signal.h>
system(s) /* run command line s */
char *s;
{
int status, pid, w, tty;
int (*istat)(), (*qstat)();
...
if ((pid = fork()) == 0) {
...
execlp("sh", "sh", "-c", s, (char*)0);
exit(127);
}
...
istat = signal(SIGINT, SIG_IGN);
qstat = signal(SIGQUIT, SIG_IGN);
while ((w = wait(&status)) != pid && w != -1)
;
if (w == -1)
status = -1;
signal(SIGINT, istat);
signal(SIGQUIT, qstat);
return status;
}
3.8.53 system.c
/*
* Safer version of system for interactive programs
*/
#include <signal.h>
#include <stdio.h>
system(s) /* run command line s */
char *s;
{
int status, pid, w, tty;
int (*istat)(), (*qstat)();
extern char *progname;
fflush(stdout);
tty = open("/dev/tty", 2);
if (tty == -1) {
fprintf (stderr, "%s: can't open /dev/ttyn", progname);
return -1;
}
if ((pid = fork()) == 0) {
close(0);
dup(tty);
close(1);
dup(tty);
close(2);
dup(tty);
close(tty);
execlp("sh", "sh", "-c", s, (char*)0);
exit(127);
}
close(tty);
istat = signal(SIGINT, SIG_IGN);
qstat = signal(SIGQUIT, SIG_IGN);
while ((w = wait(&status)) != pid && w != -1)
;
if (w == -1)
status = -1;
signal(SIGINT, istat);
signal(SIGQUIT, qstat);
return status;
}
3.8.54 timeout.c
/* timeout: set time limit on a process */
#include <stdio.h>
#include <signal.h>
int pid; /* child process id */
char *progname;
main(argc, argv)
int argc;
char *argv[];
{
int sec = 10, status, onalarm();
progname = argv[0];
if (argc > 1 && argv[1][0] == '-') {
sec = atoi(&argv[1][1]);
argc--;
argv++;
}
if (argc < 2)
error("Usage: %s [-10] command", progname);
if ((pid=fork()) == 0) {
execvp(argv[1], &argv[1]);
error("couldn't start %s", argv[1]);
}
signal(SIGALRM, onalarm);
alarm(sec);
if (wait(&status) == -1 || (status & 0177) != 0)
error("%s killed", argv[1]);
exit((status >> 8) & 0377);
}
onalarm() /* kill child when alarm arrives */
{
kill(pid, SIGKILL);
}
#include "error.c"
3.8.55 toolong
length($0) > 72 { print "Line", NR, "too long:", substr($0,1,60) }
3.8.56 ttyin1.c
ttyin() /* process response from /dev/tty (version 1) */
