systemd-delta: Only print colors when on a tty

This make systemd-delta follow the behaviour of systemctl
and journalctl.

https://bugs.freedesktop.org/show_bug.cgi?id=67656

[zj: unify color query methods between those three programs.]

1 files changed, 16 insertions, 0 deletions

diff --git a/src/shared/util.h b/src/shared/util.h
index ac999c624c..3be692ec33 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -374,6 +374,22 @@ void columns_lines_cache_reset(int _unused_ signum);
 
 bool on_tty(void);
 
+static inline const char *ansi_highlight(void) {
+        return on_tty() ? ANSI_HIGHLIGHT_ON : "";
+}
+
+static inline const char *ansi_highlight_red(void) {
+        return on_tty() ? ANSI_HIGHLIGHT_RED_ON : "";
+}
+
+static inline const char *ansi_highlight_green(void) {
+        return on_tty() ? ANSI_HIGHLIGHT_GREEN_ON : "";
+}
+
+static inline const char *ansi_highlight_off(void) {
+        return on_tty() ? ANSI_HIGHLIGHT_OFF : "";
+}
+
 int running_in_chroot(void);
 
 char *ellipsize(const char *s, size_t length, unsigned percent);