211 lines
3.6 KiB
C
211 lines
3.6 KiB
C
/*
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* Based on linux-perf/git scm
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*
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* Some modifications and simplifications for util-linux
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* by Davidlohr Bueso <dave@xxxxxxx> - March 2012.
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*/
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <err.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include "c.h"
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#include "xalloc.h"
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#include "nls.h"
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#define NULL_DEVICE "/dev/null"
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void setup_pager(void);
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static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
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struct child_process {
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const char **argv;
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pid_t pid;
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int in;
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int out;
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int err;
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unsigned no_stdin:1;
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void (*preexec_cb)(void);
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};
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static struct child_process pager_process;
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static inline void close_pair(int fd[2])
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{
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close(fd[0]);
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close(fd[1]);
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}
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static int start_command(struct child_process *cmd)
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{
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int need_in;
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int fdin[2];
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/*
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* In case of errors we must keep the promise to close FDs
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* that have been passed in via ->in and ->out.
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*/
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need_in = !cmd->no_stdin && cmd->in < 0;
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if (need_in) {
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if (pipe(fdin) < 0) {
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if (cmd->out > 0)
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close(cmd->out);
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return -1;
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}
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cmd->in = fdin[1];
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}
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fflush(NULL);
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cmd->pid = fork();
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if (!cmd->pid) {
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if (need_in) {
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dup2(fdin[0], 0);
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close_pair(fdin);
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} else if (cmd->in > 0) {
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dup2(cmd->in, 0);
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close(cmd->in);
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}
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cmd->preexec_cb();
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execvp(cmd->argv[0], (char *const*) cmd->argv);
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exit(127); /* cmd not found */
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}
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if (cmd->pid < 0) {
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if (need_in)
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close_pair(fdin);
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else if (cmd->in)
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close(cmd->in);
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return -1;
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}
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if (need_in)
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close(fdin[0]);
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else if (cmd->in)
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close(cmd->in);
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return 0;
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}
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static int wait_or_whine(pid_t pid)
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{
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for (;;) {
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int status, code;
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pid_t waiting = waitpid(pid, &status, 0);
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if (waiting < 0) {
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if (errno == EINTR)
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continue;
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err(EXIT_FAILURE, _("waitpid failed (%s)"), strerror(errno));
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}
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if (waiting != pid)
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return -1;
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if (WIFSIGNALED(status))
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return -1;
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if (!WIFEXITED(status))
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return -1;
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code = WEXITSTATUS(status);
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switch (code) {
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case 127:
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return -1;
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case 0:
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return 0;
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default:
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return -1;
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}
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}
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}
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static int finish_command(struct child_process *cmd)
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{
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return wait_or_whine(cmd->pid);
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}
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static void pager_preexec(void)
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{
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/*
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* Work around bug in "less" by not starting it until we
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* have real input
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*/
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fd_set in;
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FD_ZERO(&in);
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FD_SET(0, &in);
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select(1, &in, NULL, &in, NULL);
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setenv("LESS", "FRSX", 0);
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}
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static void wait_for_pager(void)
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{
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fflush(stdout);
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fflush(stderr);
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/* signal EOF to pager */
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close(1);
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close(2);
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finish_command(&pager_process);
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}
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static void wait_for_pager_signal(int signo)
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{
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wait_for_pager();
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raise(signo);
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}
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void setup_pager(void)
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{
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const char *pager = getenv("PAGER");
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if (!isatty(1))
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return;
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if (!pager)
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pager = "less";
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else if (!*pager || !strcmp(pager, "cat"))
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return;
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/* spawn the pager */
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pager_argv[2] = pager;
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pager_process.argv = pager_argv;
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pager_process.in = -1;
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pager_process.preexec_cb = pager_preexec;
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if (start_command(&pager_process))
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return;
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/* original process continues, but writes to the pipe */
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dup2(pager_process.in, 1);
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if (isatty(2))
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dup2(pager_process.in, 2);
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close(pager_process.in);
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/* this makes sure that the parent terminates after the pager */
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signal(SIGINT, wait_for_pager_signal);
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signal(SIGHUP, wait_for_pager_signal);
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signal(SIGTERM, wait_for_pager_signal);
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signal(SIGQUIT, wait_for_pager_signal);
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signal(SIGPIPE, wait_for_pager_signal);
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atexit(wait_for_pager);
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}
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#ifdef TEST_PROGRAM
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#define MAX 255
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int main(int argc __attribute__ ((__unused__)),
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char *argv[] __attribute__ ((__unused__)))
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{
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int i;
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setup_pager();
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for (i = 0; i < MAX; i++)
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printf("%d\n", i);
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return EXIT_SUCCESS;
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}
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#endif /* TEST_PROGRAM */
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