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#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
pid_t
pipeto(const char *cmdline)
{
int pipe0[2]; // stdout -> stdin
int pipe1[2]; // child errno -> parent
pid_t pid;
if (pipe(pipe0) < 0)
return -1;
if (pipe(pipe1) < 0)
return -1;
pid = fork();
if (pid < 0) {
return -1;
} else if (pid == 0) { // in child
close(pipe1[0]);
// close errno pipe on successful exec
fcntl(pipe1[1], F_SETFD, FD_CLOEXEC);
if (dup2(pipe0[0], 0) < 0)
exit(111);
close(pipe0[0]);
close(pipe0[1]);
// split cmdline, just on spaces
char *argv[16];
int argc = 0;
char *cp = strdup(cmdline);
if (!cp)
exit(111);
while (argc < 16 && *cp) {
argv[argc++] = cp;
cp = strchr(cp, ' ');
if (!cp)
break;
*cp++ = 0;
while (*cp == ' ')
cp++;
}
argv[argc] = 0;
if (argv[0])
execvp(argv[0], argv);
else
errno = EINVAL;
// execvp failed, write errno to parent
long e = errno;
if (write(pipe1[1], &e, sizeof e) < 0)
exit(111); // do a magic dance for gcc -Wunused-result
exit(111);
} else { // in parent
close(pipe1[1]);
long e;
ssize_t n = read(pipe1[0], &e, sizeof e);
if (n < 0)
e = errno;
close(pipe1[0]);
if (n == 0) {
// child executed successfully, redirect stdout to it
if (dup2(pipe0[1], 1) < 0)
return -1;
close(pipe0[0]);
close(pipe0[1]);
return pid;
} else {
errno = e;
return -1;
}
}
// return pid;
}
int
pipeclose(pid_t pid)
{
int s;
fflush(0);
close(1);
waitpid(pid, &s, 0);
return s;
}
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