int pager_open(bool jump_to_end) {
int fd[2];
const char *pager;
pid_t parent_pid;
int r;
if (pager_pid > 0)
return 1;
if ((pager = getenv("SYSTEMD_PAGER")) || (pager = getenv("PAGER")))
if (!*pager || streq(pager, "cat"))
return 0;
if (!on_tty())
return 0;
/* Determine and cache number of columns before we spawn the
* pager so that we get the value from the actual tty */
columns();
if (pipe(fd) < 0)
return log_error_errno(errno, "Failed to create pager pipe: %m");
parent_pid = getpid();
pager_pid = fork();
if (pager_pid < 0) {
r = -errno;
log_error_errno(errno, "Failed to fork pager: %m");
safe_close_pair(fd);
return r;
}
/* In the child start the pager */
if (pager_pid == 0) {
const char* less_opts;
dup2(fd[0], STDIN_FILENO);
safe_close_pair(fd);
less_opts = getenv("SYSTEMD_LESS");
if (!less_opts)
less_opts = "FRSXMK";
if (jump_to_end)
less_opts = strjoina(less_opts, " +G");
setenv("LESS", less_opts, 1);
/* Make sure the pager goes away when the parent dies */
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
_exit(EXIT_FAILURE);
/* Check whether our parent died before we were able
* to set the death signal */
if (getppid() != parent_pid)
_exit(EXIT_SUCCESS);
if (pager) {
execlp(pager, pager, NULL);
execl("/bin/sh", "sh", "-c", pager, NULL);
}
/* Debian's alternatives command for pagers is
* called 'pager'. Note that we do not call
* sensible-pagers here, since that is just a
* shell script that implements a logic that
* is similar to this one anyway, but is
* Debian-specific. */
execlp("pager", "pager", NULL);
execlp("less", "less", NULL);
execlp("more", "more", NULL);
pager_fallback();
/* not reached */
}
/* Return in the parent */
if (dup2(fd[1], STDOUT_FILENO) < 0)
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
safe_close_pair(fd);
return 1;
}
int pager_open(bool no_pager, bool jump_to_end) {
_cleanup_close_pair_ int fd[2] = { -1, -1 };
const char *pager;
pid_t parent_pid;
if (no_pager)
return 0;
if (pager_pid > 0)
return 1;
if (terminal_is_dumb())
return 0;
pager = getenv("SYSTEMD_PAGER");
if (!pager)
pager = getenv("PAGER");
/* If the pager is explicitly turned off, honour it */
if (pager && STR_IN_SET(pager, "", "cat"))
return 0;
/* Determine and cache number of columns before we spawn the
* pager so that we get the value from the actual tty */
(void) columns();
if (pipe(fd) < 0)
return log_error_errno(errno, "Failed to create pager pipe: %m");
parent_pid = getpid();
pager_pid = fork();
if (pager_pid < 0)
return log_error_errno(errno, "Failed to fork pager: %m");
/* In the child start the pager */
if (pager_pid == 0) {
const char* less_opts, *less_charset;
(void) reset_all_signal_handlers();
(void) reset_signal_mask();
(void) dup2(fd[0], STDIN_FILENO);
safe_close_pair(fd);
/* Initialize a good set of less options */
less_opts = getenv("SYSTEMD_LESS");
if (!less_opts)
less_opts = "FRSXMK";
if (jump_to_end)
less_opts = strjoina(less_opts, " +G");
setenv("LESS", less_opts, 1);
/* Initialize a good charset for less. This is
* particularly important if we output UTF-8
* characters. */
less_charset = getenv("SYSTEMD_LESSCHARSET");
if (!less_charset && is_locale_utf8())
less_charset = "utf-8";
if (less_charset)
setenv("LESSCHARSET", less_charset, 1);
/* Make sure the pager goes away when the parent dies */
if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
_exit(EXIT_FAILURE);
/* Check whether our parent died before we were able
* to set the death signal */
if (getppid() != parent_pid)
_exit(EXIT_SUCCESS);
if (pager) {
execlp(pager, pager, NULL);
execl("/bin/sh", "sh", "-c", pager, NULL);
}
/* Debian's alternatives command for pagers is
* called 'pager'. Note that we do not call
* sensible-pagers here, since that is just a
* shell script that implements a logic that
* is similar to this one anyway, but is
* Debian-specific. */
execlp("pager", "pager", NULL);
execlp("less", "less", NULL);
execlp("more", "more", NULL);
pager_fallback();
/* not reached */
}
/* Return in the parent */
if (dup2(fd[1], STDOUT_FILENO) < 0)
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
if (dup2(fd[1], STDERR_FILENO) < 0)
return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
return 1;
}
