agetty: add --show-issue to review issue output

Let's make life easier for admins and allow to review issue file
output on the current terminal without all full agetty execution. Use
case is pretty simple:

 # $EDITOR /etc/issue
 # agetty --show-issue

Addresses: https://github.com/karelzak/util-linux/issues/828
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/term-utils/agetty.8 b/term-utils/agetty.8
index eb6cb334106abb717042f39bb629786fe97483f4..c6af995dc1202e9392acb97e042726dec79319fb 100644 (file)
--- a/term-utils/agetty.8
+++ b/term-utils/agetty.8
@@ -124,6 +124,12 @@ extension in version-sort order from the directory.  This allows custom
 messages to be displayed on different terminals.  The
 \-\-noissue option will override this option.
 .TP
+\-\-show\-issue
+Display the current issue file (or other) on the current terminal and exit.
+Use this option to review the current setting, it is not designed for any other
+purpose.  Note that output may use some default or incomplete information as 
+proper output depends on terminal and agetty command line.
+.TP
 \-h, \-\-flow\-control
 Enable hardware (RTS/CTS) flow control.  It is left up to the
 application to disable software (XON/XOFF) flow protocol where
@@ -349,7 +355,7 @@ The default issue file is \fI/etc/issue\fP. If the file exists then agetty also
 checks for \fI/etc/issue.d\fP directory. The directory is optional extension to
 the default issue file and content of the directory is printed after
 \fI/etc/issue\fP content. If the \fI/etc/issue\fP does not exist than the
-directory is ignored. All files with .issue extension from the directory are
+directory is ignored. All files \fBwith .issue extension\fP from the directory are
 printed in version-sort order. The directory allow to maintain 3rd-party
 messages independently on the primary system \fI/etc/issue\fP file.
 
@@ -366,6 +372,9 @@ directory locations are ignored.
 
 The issue file feature is possible to completely disable by \fB\-\-noissue\fP option.
 
+It is possible to review the current issue file by \fBagetty \-\-show\-issue\fP
+on the current terminal.
+
 The issue files may contain certain escape codes to display the system name, date, time
 etcetera.  All escape codes consist of a backslash (\\) immediately
 followed by one of the characters listed below.

diff --git a/term-utils/agetty.c b/term-utils/agetty.c
index f1e5b32929feceddc48b87222e933b1c7c5a5040..a0d0876c3bf4ad320e4a06c115f917ed8b0cbef3 100644 (file)
--- a/term-utils/agetty.c
+++ b/term-utils/agetty.c
@@ -342,6 +342,8 @@ static void login_options_to_argv(char *argv[], int *argc, char *str, char *user
 static void reload_agettys(void);
 static void print_issue_file(struct issue *ie, struct options *op, struct termios *tp);
 static void eval_issue_file(struct issue *ie, struct options *op, struct termios *tp);
+static void show_issue(struct options *op);
+
 
 /* Fake hostname for ut_host specified on command line. */
 static char *fakehost;
@@ -709,6 +711,7 @@ static void parse_args(int argc, char **argv, struct options *op)
                KILL_CHARS_OPTION,
                RELOAD_OPTION,
                LIST_SPEEDS_OPTION,
+               ISSUE_SHOW_OPTION,
        };
        const struct option longopts[] = {
                {  "8bits",          no_argument,        NULL,  '8'  },
@@ -718,6 +721,7 @@ static void parse_args(int argc, char **argv, struct options *op)
                {  "delay",          required_argument,  NULL,  'd'  },
                {  "remote",         no_argument,        NULL,  'E'  },
                {  "issue-file",     required_argument,  NULL,  'f'  },
+               {  "show-issue",     no_argument,        NULL,  ISSUE_SHOW_OPTION },
                {  "flow-control",   no_argument,        NULL,  'h'  },
                {  "host",           required_argument,  NULL,  'H'  },
                {  "noissue",        no_argument,        NULL,  'i'  },
@@ -864,6 +868,10 @@ static void parse_args(int argc, char **argv, struct options *op)
                case LIST_SPEEDS_OPTION:
                        list_speeds();
                        exit(EXIT_SUCCESS);
+               case ISSUE_SHOW_OPTION:
+                       show_issue(op);
+                       exit(EXIT_SUCCESS);
+                       break;
                case VERSION_OPTION:
                        output_version();
                        exit(EXIT_SUCCESS);
@@ -1794,6 +1802,11 @@ static void eval_issue_file(struct issue *ie __attribute__((__unused__)),
                            struct termios *tp __attribute__((__unused__)))
 {
 }
+
+static void show_issue(struct options *op __attribute__((__unused__)))
+{
+}
+
 #else /* ISSUE_SUPPORT */
 
 static int issuefile_read_stream(
@@ -1816,7 +1829,6 @@ static int issuefile_read_stream(
                        putc(c, ie->output);
        }
 
-       fclose(f);
        return 0;
 }
 
@@ -1827,9 +1839,10 @@ static int issuefile_read(
        FILE *f = fopen(filename, "r" UL_CLOEXECSTR);
        int rc = 1;
 
-       if (f)
+       if (f) {
                rc = issuefile_read_stream(ie, f, op, tp);
-       fclose(f);
+               fclose(f);
+       }
        return rc;
 }
 
@@ -1954,6 +1967,27 @@ done:
        if (ie->output)
                fclose(ie->output);
 }
+
+/* This is --show-issue backend, executed by normal user on the current
+ * terminal.
+ */
+static void show_issue(struct options *op)
+{
+       struct issue ie = { .output = NULL };
+       struct termios tp;
+
+       memset(&tp, 0, sizeof(struct termios));
+       if (tcgetattr(STDIN_FILENO, &tp) < 0)
+               err(EXIT_FAILURE, _("failed to get terminal attributes: %m"));
+
+       eval_issue_file(&ie, op, &tp);
+
+       if (ie.mem_sz)
+               write_all(STDOUT_FILENO, ie.mem, ie.mem_sz);
+
+       free(ie.mem);
+}
+
 #endif /* ISSUE_SUPPORT */
 
 /* Show login prompt, optionally preceded by /etc/issue contents. */
@@ -2377,6 +2411,7 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(_(" -c, --noreset              do not reset control mode\n"), out);
        fputs(_(" -E, --remote               use -r <hostname> for login(1)\n"), out);
        fputs(_(" -f, --issue-file <file>    display issue file\n"), out);
+       fputs(_("     --show-issue           display issue file and exit\n"), out);
        fputs(_(" -h, --flow-control         enable hardware flow control\n"), out);
        fputs(_(" -H, --host <hostname>      specify login host\n"), out);
        fputs(_(" -i, --noissue              do not display issue file\n"), out);