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-rw-r--r--src/shared/pager.c270
1 files changed, 270 insertions, 0 deletions
diff --git a/src/shared/pager.c b/src/shared/pager.c
new file mode 100644
index 0000000000..88d9ef349e
--- /dev/null
+++ b/src/shared/pager.c
@@ -0,0 +1,270 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "copy.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "io-util.h"
+#include "locale-util.h"
+#include "log.h"
+#include "macro.h"
+#include "pager.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+
+static pid_t pager_pid = 0;
+
+static int stored_stdout = -1;
+static int stored_stderr = -1;
+static bool stdout_redirected = false;
+static bool stderr_redirected = false;
+
+_noreturn_ static void pager_fallback(void) {
+ int r;
+
+ r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, (uint64_t) -1, 0);
+ if (r < 0) {
+ log_error_errno(r, "Internal pager failed: %m");
+ _exit(EXIT_FAILURE);
+ }
+
+ _exit(EXIT_SUCCESS);
+}
+
+static int no_quit_on_interrupt(int exe_name_fd, const char *less_opts) {
+ _cleanup_fclose_ FILE *file = NULL;
+ _cleanup_free_ char *line = NULL;
+ int r;
+
+ assert(exe_name_fd >= 0);
+ assert(less_opts);
+
+ /* This takes ownership of exe_name_fd */
+ file = fdopen(exe_name_fd, "r");
+ if (!file) {
+ safe_close(exe_name_fd);
+ return log_debug_errno(errno, "Failed to create FILE object: %m");
+ }
+
+ /* Find the last line */
+ for (;;) {
+ _cleanup_free_ char *t = NULL;
+
+ r = read_line(file, LONG_LINE_MAX, &t);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ break;
+
+ free_and_replace(line, t);
+ }
+
+ /* We only treat "less" specially.
+ * Return true whenever option K is *not* set. */
+ r = streq_ptr(line, "less") && !strchr(less_opts, 'K');
+
+ log_debug("Pager executable is \"%s\", options \"%s\", quit_on_interrupt: %s",
+ strnull(line), less_opts, yes_no(!r));
+ return r;
+}
+
+int pager_open(PagerFlags flags) {
+ _cleanup_close_pair_ int fd[2] = { -1, -1 }, exe_name_pipe[2] = { -1, -1 };
+ _cleanup_strv_free_ char **pager_args = NULL;
+ const char *pager, *less_opts;
+ int r;
+
+ if (flags & PAGER_DISABLE)
+ return 0;
+
+ if (pager_pid > 0)
+ return 1;
+
+ if (terminal_is_dumb())
+ return 0;
+
+ if (!is_main_thread())
+ return -EPERM;
+
+ pager = getenv("SYSTEMD_PAGER");
+ if (!pager)
+ pager = getenv("PAGER");
+
+ if (pager) {
+ pager_args = strv_split(pager, WHITESPACE);
+ if (!pager_args)
+ return -ENOMEM;
+
+ /* If the pager is explicitly turned off, honour it */
+ if (strv_isempty(pager_args) || strv_equal(pager_args, STRV_MAKE("cat")))
+ return 0;
+ }
+
+ /* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
+ * actual tty */
+ (void) columns();
+ (void) lines();
+
+ if (pipe2(fd, O_CLOEXEC) < 0)
+ return log_error_errno(errno, "Failed to create pager pipe: %m");
+
+ /* This is a pipe to feed the name of the executed pager binary into the parent */
+ if (pipe2(exe_name_pipe, O_CLOEXEC) < 0)
+ return log_error_errno(errno, "Failed to create exe_name pipe: %m");
+
+ /* Initialize a good set of less options */
+ less_opts = getenv("SYSTEMD_LESS");
+ if (!less_opts)
+ less_opts = "FRSXMK";
+ if (flags & PAGER_JUMP_TO_END)
+ less_opts = strjoina(less_opts, " +G");
+
+ r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pager_pid);
+ if (r < 0)
+ return r;
+ if (r == 0) {
+ const char *less_charset, *exe;
+
+ /* In the child start the pager */
+
+ (void) dup2(fd[0], STDIN_FILENO);
+ safe_close_pair(fd);
+
+ if (setenv("LESS", less_opts, 1) < 0)
+ _exit(EXIT_FAILURE);
+
+ /* 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) < 0)
+ _exit(EXIT_FAILURE);
+
+ if (pager_args) {
+ if (loop_write(exe_name_pipe[1], pager_args[0], strlen(pager_args[0]) + 1, false) < 0)
+ _exit(EXIT_FAILURE);
+
+ execvp(pager_args[0], pager_args);
+ }
+
+ /* 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. */
+ FOREACH_STRING(exe, "pager", "less", "more") {
+ if (loop_write(exe_name_pipe[1], exe, strlen(exe) + 1, false) < 0)
+ _exit(EXIT_FAILURE);
+ execlp(exe, exe, NULL);
+ }
+
+ if (loop_write(exe_name_pipe[1], "(built-in)", strlen("(built-in") + 1, false) < 0)
+ _exit(EXIT_FAILURE);
+ pager_fallback();
+ /* not reached */
+ }
+
+ /* Return in the parent */
+ stored_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
+ if (dup2(fd[1], STDOUT_FILENO) < 0) {
+ stored_stdout = safe_close(stored_stdout);
+ return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
+ }
+ stdout_redirected = true;
+
+ stored_stderr = fcntl(STDERR_FILENO, F_DUPFD_CLOEXEC, 3);
+ if (dup2(fd[1], STDERR_FILENO) < 0) {
+ stored_stderr = safe_close(stored_stderr);
+ return log_error_errno(errno, "Failed to duplicate pager pipe: %m");
+ }
+ stderr_redirected = true;
+
+ exe_name_pipe[1] = safe_close(exe_name_pipe[1]);
+
+ r = no_quit_on_interrupt(TAKE_FD(exe_name_pipe[0]), less_opts);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ (void) ignore_signals(SIGINT, -1);
+
+ return 1;
+}
+
+void pager_close(void) {
+
+ if (pager_pid <= 0)
+ return;
+
+ /* Inform pager that we are done */
+ (void) fflush(stdout);
+ if (stdout_redirected)
+ if (stored_stdout < 0 || dup2(stored_stdout, STDOUT_FILENO) < 0)
+ (void) close(STDOUT_FILENO);
+ stored_stdout = safe_close(stored_stdout);
+ (void) fflush(stderr);
+ if (stderr_redirected)
+ if (stored_stderr < 0 || dup2(stored_stderr, STDERR_FILENO) < 0)
+ (void) close(STDERR_FILENO);
+ stored_stderr = safe_close(stored_stderr);
+ stdout_redirected = stderr_redirected = false;
+
+ (void) kill(pager_pid, SIGCONT);
+ (void) wait_for_terminate(pager_pid, NULL);
+ pager_pid = 0;
+}
+
+bool pager_have(void) {
+ return pager_pid > 0;
+}
+
+int show_man_page(const char *desc, bool null_stdio) {
+ const char *args[4] = { "man", NULL, NULL, NULL };
+ char *e = NULL;
+ pid_t pid;
+ size_t k;
+ int r;
+
+ k = strlen(desc);
+
+ if (desc[k-1] == ')')
+ e = strrchr(desc, '(');
+
+ if (e) {
+ char *page = NULL, *section = NULL;
+
+ page = strndupa(desc, e - desc);
+ section = strndupa(e + 1, desc + k - e - 2);
+
+ args[1] = section;
+ args[2] = page;
+ } else
+ args[1] = desc;
+
+ r = safe_fork("(man)", FORK_RESET_SIGNALS|FORK_DEATHSIG|(null_stdio ? FORK_NULL_STDIO : 0)|FORK_LOG, &pid);
+ if (r < 0)
+ return r;
+ if (r == 0) {
+ /* Child */
+ execvp(args[0], (char**) args);
+ log_error_errno(errno, "Failed to execute man: %m");
+ _exit(EXIT_FAILURE);
+ }
+
+ return wait_for_terminate_and_check(NULL, pid, 0);
+}
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