Prep v239: Mirror upstream and move pager.[hc] from shared to basic.

1 files changed, 208 insertions, 0 deletions

diff --git a/src/basic/pager.c b/src/basic/pager.c
new file mode 100644
index 000000000..c0ad0bb3b
--- /dev/null
+++ b/src/basic/pager.c
@@ -0,0 +1,208 @@
+/* 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 "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);
+}
+
+int pager_open(bool no_pager, bool jump_to_end) {
+        _cleanup_close_pair_ int fd[2] = { -1, -1 };
+        const char *pager;
+        int r;
+
+        if (no_pager)
+                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 the pager is explicitly turned off, honour it */
+        if (pager && STR_IN_SET(pager, "", "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");
+
+        r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pager_pid);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                const char* less_opts, *less_charset;
+
+                /* In the child start the pager */
+
+                (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");
+                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) {
+                        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 */
+        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;
+
+        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;
+}
+
+#if 0 /// UNNEEDED by elogind
+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);
+}
+#endif // 0