systemctl: show original contents when editing unit

A comment indicates the start of the new contents of the override file,
and another indicates that lines following it will be discarded once
editing is finished.
The contents of the unit file and drop-ins are listed out after this
last marker.

Adds WRITE_STRING_FILE_TRUNCATE to set O_TRUNC when opening a file.

Thanks to cgzones for providing the required SELinux function calls.

Co-authored-by: Christian Göttsche <cgzones@googlemail.com>

diff --git a/TODO b/TODO
index b509ee2594da71bcf039007d4882479a3b34afbb..4c10401e4f703f1333645d3db8613cfcf19ba266 100644 (file)
--- a/TODO
+++ b/TODO
@@ -813,9 +813,6 @@ Features:
 
 * systemctl: if some operation fails, show log output?
 
-* systemctl edit: use equivalent of cat() to insert existing config as a comment, prepended with #.
-  Upon editor exit, lines with one # are removed, lines with two # are left with one #, etc.
-
 * exponential backoff in timesyncd when we cannot reach a server
 
 * timesyncd: add ugly bus calls to set NTP servers per-interface, for usage by NM

diff --git a/src/systemctl/systemctl-edit.c b/src/systemctl/systemctl-edit.c
index f4b256335ae394b8c8cf5b3f3edf9e7283d2abd1..d6f595d47731a0d1e72835ff82314ae5ab38a0ef 100644 (file)
--- a/src/systemctl/systemctl-edit.c
+++ b/src/systemctl/systemctl-edit.c
@@ -2,6 +2,8 @@
 
 #include "bus-error.h"
 #include "copy.h"
+#include "fd-util.h"
+#include "fileio.h"
 #include "fs-util.h"
 #include "mkdir.h"
 #include "pager.h"
@@ -17,6 +19,9 @@
 #include "terminal-util.h"
 #include "tmpfile-util.h"
 
+#define EDIT_MARKER_START "### Anything between here and the comment below will become the new contents of the file"
+#define EDIT_MARKER_END "### Lines below this comment will be discarded"
+
 int cat(int argc, char *argv[], void *userdata) {
         _cleanup_(hashmap_freep) Hashmap *cached_name_map = NULL, *cached_id_map = NULL;
         _cleanup_(lookup_paths_free) LookupPaths lp = {};
@@ -106,12 +111,11 @@ int cat(int argc, char *argv[], void *userdata) {
         return rc;
 }
 
-static int create_edit_temp_file(const char *new_path, const char *original_path, char **ret_tmp_fn) {
+static int create_edit_temp_file(const char *new_path, const char *original_path, char ** const original_unit_paths, char **ret_tmp_fn) {
         _cleanup_free_ char *t = NULL;
         int r;
 
         assert(new_path);
-        assert(original_path);
         assert(ret_tmp_fn);
 
         r = tempfn_random(new_path, NULL, &t);
@@ -122,25 +126,78 @@ static int create_edit_temp_file(const char *new_path, const char *original_path
         if (r < 0)
                 return log_error_errno(r, "Failed to create directories for \"%s\": %m", new_path);
 
-        r = mac_selinux_create_file_prepare(original_path, S_IFREG);
-        if (r < 0)
-                return r;
+        if (original_path) {
+                r = mac_selinux_create_file_prepare(new_path, S_IFREG);
+                if (r < 0)
+                        return r;
 
-        r = copy_file(original_path, t, 0, 0644, 0, 0, COPY_REFLINK);
-        if (r == -ENOENT) {
+                r = copy_file(original_path, t, 0, 0644, 0, 0, COPY_REFLINK);
+                if (r == -ENOENT) {
+                        r = touch(t);
+                        mac_selinux_create_file_clear();
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create temporary file \"%s\": %m", t);
+                } else {
+                        mac_selinux_create_file_clear();
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create temporary file for \"%s\": %m", new_path);
+                }
+        } else if (original_unit_paths) {
+                _cleanup_free_ char *new_contents = NULL;
+                _cleanup_fclose_ FILE *f = NULL;
+                char **path;
+                size_t size;
 
-                r = touch(t);
+                r = mac_selinux_create_file_prepare(new_path, S_IFREG);
+                if (r < 0)
+                        return r;
 
+                f = fopen(t, "we");
                 mac_selinux_create_file_clear();
+                if (!f)
+                        return log_error_errno(errno, "Failed to open \"%s\": %m", t);
 
+                r = fchmod(fileno(f), 0644);
                 if (r < 0)
-                        return log_error_errno(r, "Failed to create temporary file \"%s\": %m", t);
-
-        } else {
-                mac_selinux_create_file_clear();
+                        return log_error_errno(errno, "Failed to change mode of \"%s\": %m", t);
+
+                r = read_full_file(new_path, &new_contents, &size);
+                if (r < 0 && r != -ENOENT)
+                        return log_error_errno(r, "Failed to read \"%s\": %m", new_path);
+
+                fprintf(f,
+                        "### Editing %s\n"
+                        EDIT_MARKER_START
+                        "\n\n%s%s\n"
+                        EDIT_MARKER_END,
+                        new_path,
+                        strempty(new_contents),
+                        new_contents && endswith(new_contents, "\n") ? "" : "\n");
+
+                /* Add a comment with the contents of the original unit files */
+                STRV_FOREACH(path, original_unit_paths) {
+                        _cleanup_free_ char *contents = NULL;
+
+                        /* Skip the file that's being edited */
+                        if (path_equal(*path, new_path))
+                                continue;
+
+                        r = read_full_file(*path, &contents, &size);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to read \"%s\": %m", *path);
+
+                        fprintf(f, "\n\n### %s", *path);
+                        if (!isempty(contents)) {
+                                contents = strreplace(strstrip(contents), "\n", "\n# ");
+                                if (!contents)
+                                        return log_oom();
+                                fprintf(f, "\n# %s", contents);
+                        }
+                }
 
+                r = fflush_and_check(f);
                 if (r < 0)
-                         return log_error_errno(r, "Failed to create temporary file for \"%s\": %m", new_path);
+                        return log_error_errno(r, "Failed to create temporary file \"%s\": %m", t);
         }
 
         *ret_tmp_fn = TAKE_PTR(t);
@@ -185,6 +242,7 @@ static int unit_file_create_new(
                 const LookupPaths *paths,
                 const char *unit_name,
                 const char *suffix,
+                char ** const original_unit_paths,
                 char **ret_new_path,
                 char **ret_tmp_path) {
 
@@ -201,7 +259,7 @@ static int unit_file_create_new(
         if (r < 0)
                 return r;
 
-        r = create_edit_temp_file(new_path, new_path, &tmp_path);
+        r = create_edit_temp_file(new_path, NULL, original_unit_paths, &tmp_path);
         if (r < 0)
                 return r;
 
@@ -240,7 +298,7 @@ static int unit_file_create_copy(
                         return log_warning_errno(SYNTHETIC_ERRNO(EKEYREJECTED), "%s skipped.", unit_name);
         }
 
-        r = create_edit_temp_file(new_path, fragment_path, &tmp_path);
+        r = create_edit_temp_file(new_path, fragment_path, NULL, &tmp_path);
         if (r < 0)
                 return r;
 
@@ -332,9 +390,10 @@ static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
 
         STRV_FOREACH(name, names) {
                 _cleanup_free_ char *path = NULL, *new_path = NULL, *tmp_path = NULL, *tmp_name = NULL;
+                _cleanup_strv_free_ char **unit_paths = NULL;
                 const char *unit_name;
 
-                r = unit_find_paths(bus, *name, &lp, false, &cached_name_map, &cached_id_map, &path, NULL);
+                r = unit_find_paths(bus, *name, &lp, false, &cached_name_map, &cached_id_map, &path, &unit_paths);
                 if (r == -EKEYREJECTED) {
                         /* If loading of the unit failed server side complete, then the server won't tell us
                          * the unit file path. In that case, find the file client side. */
@@ -361,7 +420,7 @@ static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
                         unit_name = *name;
                         r = unit_file_create_new(&lp, unit_name,
                                                  arg_full ? NULL : ".d/override.conf",
-                                                 &new_path, &tmp_path);
+                                                 NULL, &new_path, &tmp_path);
                 } else {
                         assert(path);
 
@@ -384,8 +443,13 @@ static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
 
                         if (arg_full)
                                 r = unit_file_create_copy(&lp, unit_name, path, &new_path, &tmp_path);
-                        else
-                                r = unit_file_create_new(&lp, unit_name, ".d/override.conf", &new_path, &tmp_path);
+                        else {
+                                r = strv_prepend(&unit_paths, path);
+                                if (r < 0)
+                                        return log_oom();
+
+                                r = unit_file_create_new(&lp, unit_name, ".d/override.conf", unit_paths, &new_path, &tmp_path);
+                        }
                 }
                 if (r < 0)
                         return r;
@@ -400,6 +464,40 @@ static int find_paths_to_edit(sd_bus *bus, char **names, char ***paths) {
         return 0;
 }
 
+static int trim_edit_markers(const char *path) {
+        _cleanup_free_ char *contents = NULL;
+        char *contents_start = NULL;
+        const char *contents_end = NULL;
+        size_t size;
+        int r;
+
+        /* Trim out the lines between the two markers */
+        r = read_full_file(path, &contents, &size);
+        if (r < 0)
+                return log_error_errno(r, "Failed to read temporary file \"%s\": %m", path);
+
+        contents_start = strstr(contents, EDIT_MARKER_START);
+        if (contents_start)
+                contents_start += strlen(EDIT_MARKER_START);
+        else
+                contents_start = contents;
+
+        contents_end = strstr(contents_start, EDIT_MARKER_END);
+        if (contents_end)
+                strshorten(contents_start, contents_end - contents_start);
+
+        contents_start = strstrip(contents_start);
+
+        /* Write new contents if the trimming actually changed anything */
+        if (strlen(contents) != size) {
+                r = write_string_file(path, contents_start, WRITE_STRING_FILE_CREATE | WRITE_STRING_FILE_TRUNCATE | WRITE_STRING_FILE_AVOID_NEWLINE);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to modify temporary file \"%s\": %m", path);
+        }
+
+        return 0;
+}
+
 int edit(int argc, char *argv[], void *userdata) {
         _cleanup_(lookup_paths_free) LookupPaths lp = {};
         _cleanup_strv_free_ char **names = NULL;
@@ -452,6 +550,10 @@ int edit(int argc, char *argv[], void *userdata) {
         STRV_FOREACH_PAIR(original, tmp, paths) {
                 /* If the temporary file is empty we ignore it. This allows the user to cancel the
                  * modification. */
+                r = trim_edit_markers(*tmp);
+                if (r < 0)
+                        continue;
+
                 if (null_or_empty_path(*tmp)) {
                         log_warning("Editing \"%s\" canceled: temporary file is empty.", *original);
                         continue;