man: make width selection more thorough; explain how to override it

Fedora's "man CMD >file" still uses terminal width, not 80 (but disables formatting),
this change mimics that.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 38 insertions, 9 deletions

diff --git a/libbb/xfuncs.c b/libbb/xfuncs.c
index 3f9a84ad4..45650edba 100644
--- a/libbb/xfuncs.c
+++ b/libbb/xfuncs.c
@@ -237,16 +237,27 @@ ssize_t FAST_FUNC full_write2_str(const char *str)
 
 static int wh_helper(int value, int def_val, const char *env_name, int *err)
 {
-        if (value == 0) {
-                char *s = getenv(env_name);
-                if (s) {
-                        value = atoi(s);
-                        /* If LINES/COLUMNS are set, pretend that there is
-                         * no error getting w/h, this prevents some ugly
-                         * cursor tricks by our callers */
-                        *err = 0;
-                }
+        /* Envvars override even if "value" from ioctl is valid (>0).
+         * Rationale: it's impossible to guess what user wants.
+         * For example: "man CMD | ...": should "man" format output
+         * to stdout's width? stdin's width? /dev/tty's width? 80 chars?
+         * We _cant_ know it. If "..." saves text for e.g. email,
+         * then it's probably 80 chars.
+         * If "..." is, say, "grep -v DISCARD | $PAGER", then user
+         * would prefer his tty's width to be used!
+         *
+         * Since we don't know, at least allow user to do this:
+         * "COLUMNS=80 man CMD | ..."
+         */
+        char *s = getenv(env_name);
+        if (s) {
+                value = atoi(s);
+                /* If LINES/COLUMNS are set, pretend that there is
+                 * no error getting w/h, this prevents some ugly
+                 * cursor tricks by our callers */
+                *err = 0;
         }
+
         if (value <= 1 || value >= 30000)
                 value = def_val;
         return value;
@@ -258,6 +269,20 @@ int FAST_FUNC get_terminal_width_height(int fd, unsigned *width, unsigned *heigh
 {
         struct winsize win;
         int err;
+        int close_me = -1;
+
+        if (fd == -1) {
+                if (isatty(STDOUT_FILENO))
+                        fd = STDOUT_FILENO;
+                else
+                if (isatty(STDERR_FILENO))
+                        fd = STDERR_FILENO;
+                else
+                if (isatty(STDIN_FILENO))
+                        fd = STDIN_FILENO;
+                else
+                        close_me = fd = open("/dev/tty", O_RDONLY);
+        }
 
         win.ws_row = 0;
         win.ws_col = 0;
@@ -268,6 +293,10 @@ int FAST_FUNC get_terminal_width_height(int fd, unsigned *width, unsigned *heigh
                 *height = wh_helper(win.ws_row, 24, "LINES", &err);
         if (width)
                 *width = wh_helper(win.ws_col, 80, "COLUMNS", &err);
+
+        if (close_me >= 0)
+                close(close_me);
+
         return err;
 }
 int FAST_FUNC get_terminal_width(int fd)