pager: don't start pager if the terminal is explicitly set to TERM=dumb

As suggested here:

https://bugs.freedesktop.org/show_bug.cgi?id=64737#c8

This adds a new call terminal_is_dumb() and makes use of this where
appropriate.

2 files changed, 15 insertions, 3 deletions

diff --git a/src/basic/terminal-util.c b/src/basic/terminal-util.c
index 2b90f2e5a1..d8cca55378 100644
--- a/src/basic/terminal-util.c
+++ b/src/basic/terminal-util.c
@@ -1193,6 +1193,19 @@ int open_terminal_in_namespace(pid_t pid, const char *name, int mode) {
         return receive_one_fd(pair[0], 0);
 }
 
+bool terminal_is_dumb(void) {
+        const char *e;
+
+        if (!on_tty())
+                return true;
+
+        e = getenv("TERM");
+        if (!e)
+                return true;
+
+        return streq(e, "dumb");
+}
+
 bool colors_enabled(void) {
         static int enabled = -1;
 
@@ -1202,10 +1215,8 @@ bool colors_enabled(void) {
                 colors = getenv("SYSTEMD_COLORS");
                 if (colors)
                         enabled = parse_boolean(colors) != 0;
-                else if (streq_ptr(getenv("TERM"), "dumb"))
-                        enabled = false;
                 else
-                        enabled = on_tty();
+                        enabled = !terminal_is_dumb();
         }
 
         return enabled;
diff --git a/src/basic/terminal-util.h b/src/basic/terminal-util.h
index b449370974..169ab772ff 100644
--- a/src/basic/terminal-util.h
+++ b/src/basic/terminal-util.h
@@ -80,6 +80,7 @@ unsigned lines(void);
 void columns_lines_cache_reset(int _unused_ signum);
 
 bool on_tty(void);
+bool terminal_is_dumb(void);
 bool colors_enabled(void);
 
 static inline const char *ansi_underline(void) {