man: allow nroff and tbl commands be overridden; unmangle writing to files

Parse this in config files:
	 DEFINE col ...
	 DEFINE tbl ...
	 DEFINE nroff ...
Add width options to nroff command line.
Use "tbl", not "gtbl", as default tbl command.
Export GROFF_NO_SGR=1 and use "col -b -p -x" instead of pager when writing to file.

function                                             old     new   delta
man_main                                             735     863    +128
if_redefined                                           -      64     +64
show_manpage                                         199     169     -30
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 192/-30)           Total: 162 bytes

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

1 files changed, 79 insertions, 25 deletions

diff --git a/miscutils/man.c b/miscutils/man.c
index f705dd31e..01382c4d7 100644
--- a/miscutils/man.c
+++ b/miscutils/man.c
@@ -11,6 +11,7 @@
 //usage:     "\n        -w      Show page locations"
 
 #include "libbb.h"
+#include "common_bufsiz.h"
 
 enum {
         OPT_a = 1, /* all */
@@ -18,7 +19,6 @@ enum {
 };
 
 /* This is what I see on my desktop system being executed:
-
 (
 echo ".ll 12.4i"
 echo ".nr LL 12.4i"
@@ -28,11 +28,39 @@ echo ".\\\""
 echo ".pl \n(nlu+10"
 ) | gtbl | nroff -Tlatin1 -mandoc | less
 
-*/
+On another system I see this:
 
-static int show_manpage(const char *pager, char *man_filename, int man, int level);
+... | tbl | nroff -mandoc -rLL=<NNN>n -rLT=<NNN>n -Tutf8 | less
 
-static int run_pipe(const char *pager, char *man_filename, int man, int level)
+where <NNN> is screen width minus 5.
+Replacing "DEFINE nroff nroff -mandoc" in /etc/man_db.conf
+changes "nroff -mandoc" part; -rLL=<NNN>n, -rLT=<NNN>n and -Tutf8 parts are
+appended to the user-specified command.
+
+Redirecting to a pipe or file sets GROFF_NO_SGR=1 to prevent color escapes,
+and uses "col -b -p -x" instead of pager, this filters out backspace
+and underscore tricks.
+*/
+
+struct globals {
+        const char *col;
+        const char *tbl;
+        const char *nroff;
+        const char *pager;
+} FIX_ALIASING;
+#define G (*(struct globals*)bb_common_bufsiz1)
+#define INIT_G() do { \
+        setup_common_bufsiz(); \
+        G.col = "col"; \
+        G.tbl = "tbl"; \
+        /* replaced -Tlatin1 with -Tascii for non-UTF8 displays */; \
+        G.nroff = "nroff -mandoc -Tascii"; \
+        G.pager = ENABLE_LESS ? "less" : "more"; \
+} while (0)
+
+static int show_manpage(char *man_filename, int man, int level);
+
+static int run_pipe(char *man_filename, int man, int level)
 {
         char *cmd;
 
@@ -95,7 +123,7 @@ static int run_pipe(const char *pager, char *man_filename, int man, int level)
                 man_filename = xasprintf("%s/%s", man_filename, linkname);
                 free(line);
                 /* Note: we leak "new" man_filename string as well... */
-                if (show_manpage(pager, man_filename, man, level + 1))
+                if (show_manpage(man_filename, man, level + 1))
                         return 1;
                 /* else: show the link, it's better than nothing */
         }
@@ -103,20 +131,29 @@ static int run_pipe(const char *pager, char *man_filename, int man, int level)
  ordinary_manpage:
         close(STDIN_FILENO);
         open_zipped(man_filename, /*fail_if_not_compressed:*/ 0); /* guaranteed to use fd 0 (STDIN_FILENO) */
-        /* "2>&1" is added so that nroff errors are shown in pager too.
-         * Otherwise it may show just empty screen */
-        cmd = xasprintf(
-                /* replaced -Tlatin1 with -Tascii for non-UTF8 displays */
-                man ? "gtbl | nroff -Tascii -mandoc 2>&1 | %s"
-                    : "%s",
-                pager);
+        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);
+                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 */
+                cmd = xasprintf("%s | %s -rLL=%un -rLT=%un 2>&1 | %s",
+                                G.tbl, G.nroff, w, w,
+                                G.pager);
+        } else {
+                cmd = xstrdup(G.pager);
+        }
         system(cmd);
         free(cmd);
         return 1;
 }
 
 /* man_filename is of the form "/dir/dir/dir/name.s" */
-static int show_manpage(const char *pager, char *man_filename, int man, int level)
+static int show_manpage(char *man_filename, int man, int level)
 {
 #if SEAMLESS_COMPRESSION
         /* We leak this allocation... */
@@ -125,26 +162,26 @@ static int show_manpage(const char *pager, char *man_filename, int man, int leve
 #endif
 
 #if ENABLE_FEATURE_SEAMLESS_LZMA
-        if (run_pipe(pager, filename_with_zext, man, level))
+        if (run_pipe(filename_with_zext, man, level))
                 return 1;
 #endif
 #if ENABLE_FEATURE_SEAMLESS_XZ
         strcpy(ext, "xz");
-        if (run_pipe(pager, filename_with_zext, man, level))
+        if (run_pipe(filename_with_zext, man, level))
                 return 1;
 #endif
 #if ENABLE_FEATURE_SEAMLESS_BZ2
         strcpy(ext, "bz2");
-        if (run_pipe(pager, filename_with_zext, man, level))
+        if (run_pipe(filename_with_zext, man, level))
                 return 1;
 #endif
 #if ENABLE_FEATURE_SEAMLESS_GZ
         strcpy(ext, "gz");
-        if (run_pipe(pager, filename_with_zext, man, level))
+        if (run_pipe(filename_with_zext, man, level))
                 return 1;
 #endif
 
-        return run_pipe(pager, man_filename, man, level);
+        return run_pipe(man_filename, man, level);
 }
 
 static char **add_MANPATH(char **man_path_list, int *count_mp, char *path)
@@ -182,11 +219,20 @@ static char **add_MANPATH(char **man_path_list, int *count_mp, char *path)
         return man_path_list;
 }
 
+static const char *if_redefined(const char *var, const char *key, const char *line)
+{
+        if (!is_prefixed_with(line, key))
+                return var;
+        line += strlen(key);
+        if (!isspace(line[0]))
+                return var;
+        return xstrdup(skip_whitespace(line));
+}
+
 int man_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int man_main(int argc UNUSED_PARAM, char **argv)
 {
         parser_t *parser;
-        const char *pager = ENABLE_LESS ? "less" : "more";
         char *sec_list;
         char *cur_path, *cur_sect;
         char **man_path_list;
@@ -195,6 +241,8 @@ int man_main(int argc UNUSED_PARAM, char **argv)
         int opt, not_found;
         char *token[2];
 
+        INIT_G();
+
         opt_complementary = "-1"; /* at least one argument */
         opt = getopt32(argv, "+aw");
         argv += optind;
@@ -228,9 +276,10 @@ int man_main(int argc UNUSED_PARAM, char **argv)
                 if (!token[1])
                         continue;
                 if (strcmp("DEFINE", token[0]) == 0) {
-                        if (is_prefixed_with(token[1], "pager")) {
-                                pager = xstrdup(skip_whitespace(token[1] + 5));
-                        }
+                        G.col   = if_redefined(G.tbl  , "col",   token[1]);
+                        G.tbl   = if_redefined(G.tbl  , "tbl",   token[1]);
+                        G.nroff = if_redefined(G.nroff, "nroff", token[1]);
+                        G.pager = if_redefined(G.pager, "pager", token[1]);
                 } else
                 if (strcmp("MANDATORY_MANPATH"+10, token[0]) == 0 /* "MANPATH"? */
                  || strcmp("MANDATORY_MANPATH", token[0]) == 0
@@ -250,7 +299,12 @@ int man_main(int argc UNUSED_PARAM, char **argv)
                 if (!env_pager)
                         env_pager = getenv("PAGER");
                 if (env_pager)
-                        pager = env_pager;
+                        G.pager = env_pager;
+        }
+
+        if (!isatty(STDOUT_FILENO)) {
+                putenv((char*)"GROFF_NO_SGR=1");
+                G.pager = xasprintf("%s -b -p -x", G.col);
         }
 
         not_found = 0;
@@ -259,7 +313,7 @@ int man_main(int argc UNUSED_PARAM, char **argv)
                 cur_mp = 0;
 
                 if (strchr(*argv, '/')) {
-                        found = show_manpage(pager, *argv, /*man:*/ 1, 0);
+                        found = show_manpage(*argv, /*man:*/ 1, 0);
                         goto check_found;
                 }
                 while ((cur_path = man_path_list[cur_mp++]) != NULL) {
@@ -280,7 +334,7 @@ int man_main(int argc UNUSED_PARAM, char **argv)
                                                         sect_len, cur_sect,
                                                         *argv,
                                                         sect_len, cur_sect);
-                                        found_here = show_manpage(pager, man_filename, cat0man1, 0);
+                                        found_here = show_manpage(man_filename, cat0man1, 0);
                                         found |= found_here;
                                         cat0man1 += found_here + 1;
                                         free(man_filename);