Bug in manpage creation using dash

[charles2910]

Hi, Felix. I'm here again :-)

So Debian links /bin/sh to /bin/dash to interpret commands. The problem is dash doesn't support different locales and it's breaking the sed -E command. Invoking bash explicitily solves the problem.

The problem:

Using #!/bin/bash:

Now, is it ok to change the hashbang to /bin/bash? I'm thinking about users outside Debian (like BSD and MacOS)

[ikskuh]

This is actually a good question, i think we actually switched from bash to sh as it wasn't compatible to other systems. is sed a shell builtin in dash?

[charles2910]

we (sergiodj, samueloph and I) are suspecting the problem is in echo (which is a built in commad), not actually in sed. I'll try to do a debug session during the weekend to pinpoint the issue and report upstream. I thought "maybe I should try to report this quick and dirty fix before", but I see it might be a problem to other systems.

[charles2910]

Ok, I was able to pinpoint the problem:

Double escaping seems to solve it in sh/dash, but it put 2 backslashs in bash. I'm not sure what is the correct/expected behavior in this case.

sh/dash:

$ echo $(echo press *Return* and | sed -E -e 's#(^|[.,!? ]+)[*_]([^*_ ]+[^*_]+[^*_ ]+)[*_]($|[.,!? ])#\1\\\\fI\2\\\\fR\3#g')
press \fIReturn\fR and

bash:

charles@x1-carbon:~$ echo $(echo press *Return* and | sed -E -e 's#(^|[.,!? ]+)[*_]([^*_ ]+[^*_]+[^*_ ]+)[*_]($|[.,!? ])#\1\\\\fI\2\\\\fR\3#g')
press \\fIReturn\\fR and

[charles2910]

Now I think I've found the answer. sh and, consequently, dash interpret some escaped characters as control sequences, so an echo '\f' outputs a form feed. bash's echo defaults to ignore escaped characters unless explicitly told otherwise (-e flag).

So, my question is: should we double escape \f to comply with dash? If you agree, I can open a PR with this fix:

diff --git a/doc/gen-man.sh b/doc/gen-man.sh
index 4463c5a..52b5132 100755
--- a/doc/gen-man.sh
+++ b/doc/gen-man.sh
@@ -59,8 +59,8 @@ gem_in=$(
     # First expression replaces all [Text like this] with bold text.
     # Second expression replaces text like *This* or _this_ with italic text.
     sed -E \
-      -e 's#\[([^]]*)\]#\\fB\1\\fR#g' \
-      -e 's#(^|[.,!? ]+)[*_]([^*_ ]+[^*_]+[^*_ ]+)[*_]($|[.,!? ])#\1\\fI\2\\fR\3#g'
+      -e 's#\[([^]]*)\]#\\\\fB\1\\\\fR#g' \
+      -e 's#(^|[.,!? ]+)[*_]([^*_ ]+[^*_]+[^*_ ]+)[*_]($|[.,!? ])#\1\\\\fI\2\\\\fR\3#g'
 )
 
 # Convert gemtext to man format

[ikskuh]

Yeah, can you try make a PR?

[charles2910]

Yeah, of course!

[charles2910]

I think we can close this issue, right?