netdev - [PATCH net-next] ss: use compact output for undetected screen width

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Date:   Thu, 26 Dec 2019 14:07:09 +0100
From:   Peter Junos <petoju@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Peter Junos <petoju@...il.com>, netdev@...r.kernel.org
Subject: [PATCH net-next] ss: use compact output for undetected screen width

This change fixes calculation of width in case user pipes the output.

SS output output works correctly when stdout is a terminal. When one
pipes the output, it tries to use 80 or 160 columns. That adds a
line-break if user has terminal width of 100 chars and output is of
the similar width. No width is assumed here.

To reproduce the issue, call
ss | less
and see every other line empty if your screen is between 80 and 160
columns wide.

This second version of the patch fixes screen_width being set to arbitrary
value.

Signed-off-by: Peter Junos <petoju@...il.com>
---
 misc/ss.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/misc/ss.c b/misc/ss.c
index 95f1d37a..d5bae16d 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -1135,10 +1135,10 @@ static void buf_free_all(void)
 	buffer.chunks = 0;
 }
 
-/* Get current screen width, default to 80 columns if TIOCGWINSZ fails */
+/* Get current screen width, returns -1 if TIOCGWINSZ fails */
 static int render_screen_width(void)
 {
-	int width = 80;
+	int width = -1;
 
 	if (isatty(STDOUT_FILENO)) {
 		struct winsize w;
@@ -1159,9 +1159,15 @@ static int render_screen_width(void)
  */
 static void render_calc_width(void)
 {
-	int screen_width = render_screen_width();
+	int screen_width, first, len = 0, linecols = 0;
+	bool compact_output = false;
 	struct column *c, *eol = columns - 1;
-	int first, len = 0, linecols = 0;
+
+	screen_width = render_screen_width();
+	if (screen_width == -1) {
+		screen_width = INT_MAX;
+		compact_output = true;
+	}
 
 	/* First pass: set width for each column to measured content length */
 	for (first = 1, c = columns; c - columns < COL_MAX; c++) {
@@ -1183,6 +1189,11 @@ static void render_calc_width(void)
 			first = 0;
 	}
 
+	if (compact_output) {
+		/* Compact output, skip extending columns. */
+		return;
+	}
+
 	/* Second pass: find out newlines and distribute available spacing */
 	for (c = columns; c - columns < COL_MAX; c++) {
 		int pad, spacing, rem, last;
-- 
2.24.0