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#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#define NUM_PROCS 2
struct proc {
pid_t pid;
char *cmd;
char **argv;
int _stdin;
int _stdout;
int _stderr;
} procs[NUM_PROCS];
int fds[2];
volatile sig_atomic_t terminate = 0;
volatile sig_atomic_t sendsignal = 0;
void
gen_argv(struct proc *proc)
{
int i;
char *saveptr, *tmp;
char **argv = malloc(sizeof(char*) * 1024);
char **head = argv;
char *cmd2 = strdup(proc->cmd);
// XXX: Check malloc/strdup return
// XXX: Check for overflow in tmp
for (i = 0; i < 1024; i++)
argv[i] = NULL;
tmp = strtok_r(cmd2, " \t", &saveptr);
while (tmp != NULL) {
*(head++) = strdup(tmp);
tmp = strtok_r(NULL, " \t", &saveptr);
}
*head = NULL;
free(cmd2);
proc->argv = argv;
}
int
run_cmd(struct proc *proc)
{
pid_t cpid;
cpid = fork();
if (cpid == 0) {
if (proc->_stdin != -1) {
close(0);
dup2(proc->_stdin, 0);
}
if (proc->_stdout != -1) {
close(1);
dup2(proc->_stdout, 1);
}
if (proc->_stderr != -1) {
close(2);
dup2(proc->_stderr, 2);
}
close(fds[0]);
close(fds[1]);
execvp(proc->argv[0], proc->argv);
perror("execvp");
} else if (cpid == -1) {
// error D:
return -1;
} else {
proc->pid = cpid;
}
return 0;
}
int
have_child()
{
int i;
for (i = 0; i < NUM_PROCS; i++) {
if (procs[i].pid != -1)
return 1;
}
return 0;
}
struct proc *
proc_by_pid(pid_t pid)
{
int i;
for (i = 0; i < NUM_PROCS; i++) {
if (procs[i].pid == pid)
return &procs[i];
}
return NULL;
}
void
signal_procs()
{
int i;
for (i = 0; i < NUM_PROCS; i++) {
if (procs[i].pid != -1)
kill(procs[i].pid, sendsignal); //XXX: Check return?
}
sendsignal = 0;
}
void
handle_nonfatal(int sig, siginfo_t *siginfo, void *ucontext)
{
sendsignal = sig;
}
void
handle_fatal(int sig, siginfo_t *siginfo, void *ucontext)
{
terminate = 1;
sendsignal = sig;
}
int
main(int argc, char **argv)
{
if (argc < 2) {
fprintf(stderr, "Usage: piper <cmd1> <cmd2>\n");
return 1;
}
struct sigaction act;
memset(&act, 0, sizeof(act));
act.sa_sigaction = &handle_fatal;
act.sa_flags = SA_SIGINFO;
sigaction(SIGINT, &act, NULL);
sigaction(SIGHUP, &act, NULL);
sigaction(SIGTERM, &act, NULL);
act.sa_sigaction = &handle_nonfatal;
sigaction(SIGUSR1, &act, NULL);
sigaction(SIGUSR2, &act, NULL);
procs[0].cmd = strdup(argv[1]);
procs[1].cmd = strdup(argv[2]);
int i;
for (i = 0; i < NUM_PROCS; i++) {
procs[i].pid = -1;
procs[i]._stdin = -1;
procs[i]._stdout = -1;
procs[i]._stderr = -1;
gen_argv(&procs[i]);
}
pipe(fds); // XXX: Check return code
procs[0]._stdout = fds[1];
procs[0]._stderr = fds[1];
procs[1]._stdin = fds[0];
run_cmd(&procs[0]);
run_cmd(&procs[1]); // XXX: Check return codes
while (have_child()) {
int status;
pid_t pid;
if (sendsignal != 0)
signal_procs();
pid = wait(&status);
if (pid == -1 && errno == EINTR)
continue;
struct proc *p = proc_by_pid(pid); // XXX: Check return code
p->pid = -1;
if (!terminate)
run_cmd(p); // XXX: Check return code
}
return 0;
}
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