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>

2 files changed, 44 insertions, 16 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)
diff --git a/miscutils/man.c b/miscutils/man.c
index 01382c4d7..adb7770b4 100644
--- a/miscutils/man.c
+++ b/miscutils/man.c
@@ -9,6 +9,8 @@
 //usage:       "Format and display manual page\n"
 //usage:     "\n        -a      Display all pages"
 //usage:     "\n        -w      Show page locations"
+//usage:     "\n"
+//usage:     "\n$COLUMNS overrides output width"
 
 #include "libbb.h"
 #include "common_bufsiz.h"
@@ -53,7 +55,7 @@ struct globals {
         setup_common_bufsiz(); \
         G.col = "col"; \
         G.tbl = "tbl"; \
-        /* replaced -Tlatin1 with -Tascii for non-UTF8 displays */; \
+        /* replaced -Tlatin1 with -Tascii for non-UTF8 displays */ \
         G.nroff = "nroff -mandoc -Tascii"; \
         G.pager = ENABLE_LESS ? "less" : "more"; \
 } while (0)
@@ -132,15 +134,12 @@ static int run_pipe(char *man_filename, int man, int level)
         close(STDIN_FILENO);
         open_zipped(man_filename, /*fail_if_not_compressed:*/ 0); /* guaranteed to use fd 0 (STDIN_FILENO) */
         if (man) {
-                /* "man man" formats to screen width.
-                 * "man man >file" formats to default 80 columns.
-                 * "man man | cat" formats to default 80 columns.
-                 */
-                int w = get_terminal_width(STDOUT_FILENO);
+                int w = get_terminal_width(-1);
                 if (w > 10)
                         w -= 2;
                 /* "2>&1" is added so that nroff errors are shown in pager too.
-                 * Otherwise it may show just empty screen */
+                 * Otherwise it may show just empty screen.
+                 */
                 cmd = xasprintf("%s | %s -rLL=%un -rLT=%un 2>&1 | %s",
                                 G.tbl, G.nroff, w, w,
                                 G.pager);