Solving a problem from the previous millenium

In a world were most people rely on a webbrowser to manage their emails, and few can even orientate in their file-trees outside of their mouse oriented file "explorer/finder", fewer people, I reckon, are hit by this problem in this millenium than in the previous millenium. (On a side note I'm pleased that smartphones have re-popularised the idea of a having specific program for managing emails).

Nevertheless, I abhor having to stretch for the computer mouse and point it to this and that spot and click. While for browsing the web it is hard to find a better solution then using the mouse, but when reading mail and browsing local files, it should not be necessary. Nor should it be needed when you want to start a program. I guess my standpoint shares some ground with that of the PWMT and suckless projects, the latter from which I use dmenu and slock, both of which are in the debian package suckless-tools.

I much enjoy zathura for reading PDF-files (zathura is released by PWMT). When you keep away from mouse-oriented software, you tend to turn up in the console and in the console you manage email with mutt¹and browse file-trees with mc - and if you configure your system to let zathura view PDF-files, then you'll notice two problems:

• you email client is locked, or suspended, as long as you have the PDF-file open in the reader.
• text output from your PDF-viewer is messing up the screen, confusing the calling program (eg. mutt or mc).

Others have been annoyed by this, or similar problems, before me, see http://ruiabreu.org/2013-01-07-mutt-and-xdg.html, http://www.spocom.com/users/gjohnson/mutt/. So, what is the solution? The mailcap infrastructure already has the capabilites required to solve the problem - and it had them already from in the orginal RFC 1524 published in 1993,² so there is no point in writing new commands to do the right thing ( examples of the "write new command"-solution includes http://www.spocom.com/users/gjohnson/mutt/ who published the script mutt_bgrun for this purpose and http://ruiabreu.org/2013-01-07-mutt-and-xdg.html who wrote the program mutt-open for a similar purpose ).

Just fix the mailcap entries. OK, but how?

A suggestion on how the mailcap entry should read is this https://www.win.tue.nl/bcf/linux/software/mutt/mime.php and this is OK, but not perfect, since it creates the temporary file in an un-safe way.

This solution have the following features:

• creates a temporary file in a safe way.
• removes the temporary file, but not before zathura has exit.
• forks.
• does not confuse the calling program (ie. mutt or mc) by leaving unwanted character messages on the screen.
• does not rely on any external command not supplied by your distribution (ie. requires no custom script, or hack, in your $HOME).
• does not require that the name of PDF-file, or the path to it, contains no spaces or characters that are protected by the shell.
• does not interfere with zathuras mechanism for starting at the page that was shown on last exit (except for files residing in /tmp, if this feature is needed even for those files, then use a md5-hash of the file name instead of randomly named temporary file).

And here it is

# The Right Thing
# If the file resides in /tmp, then assume mutt as put it there, and make a
# full copy of if before forking since mutt will delete the file upon return.
# If the file does not reside in /tmp, use a safely named symlink instead of
# the real file (which name may contain spaces or characters protected by the
# shell) is in its filename or in its path.

application/pdf; { \
TEMPSYMLINK=`mktemp` \; \
rm $TEMPSYMLINK \; \
if test -L '%s' \; then \
  cp -a '%s' $TEMPSYMLINK \; \
else \
  DIR=`dirname '%s'` \; \
  if test `echo -n "$DIR" | cut -b 1-4` = "/tmp" \; then \
    cp '%s' $TEMPSYMLINK \; \
  else \
    FILE=`basename '%s'` \; \
    if test `echo -n $DIR | cut -b 1` = "/" \; then \
      ln -s "${DIR}/${FILE}" $TEMPSYMLINK \; \
    else \
      FULLDIR=`pwd`"/"${DIR} \; \
      ln -s "${FULLDIR}"/"${FILE}" $TEMPSYMLINK \; \
      fi \; \
    fi \; \
  fi \; \
  ( zathura $TEMPSYMLINK >/dev/null 2>&1 \; \
    rm $TEMPSYMLINK ) \
    & \
 } ; test=test -n "$DISPLAY"; description=Portable Document Format; nametemplate=%s.pdf;
application/x-pdf; { \
TEMPSYMLINK=`mktemp` \; \
rm $TEMPSYMLINK \; \
if test -L '%s' \; then \
  cp -a '%s' $TEMPSYMLINK \; \
else \
  DIR=`dirname '%s'` \; \
  if test `echo -n "$DIR" | cut -b 1-4` = "/tmp" \; then \
    cp '%s' $TEMPSYMLINK \; \
  else \
    FILE=`basename '%s'` \; \
    if test `echo -n $DIR | cut -b 1` = "/" \; then \
      ln -s "${DIR}/${FILE}" $TEMPSYMLINK \; \
    else \
      FULLDIR=`pwd`"/"${DIR} \; \
      ln -s "${FULLDIR}"/"${FILE}" $TEMPSYMLINK \; \
      fi \; \
    fi \; \
  fi \; \
  ( zathura $TEMPSYMLINK >/dev/null 2>&1 \; \
    rm $TEMPSYMLINK ) \
    & \
 } ; test=test -n "$DISPLAY"; description=Portable Document Format; nametemplate=%s.pdf;

And, for comparision, here are other mailcap entries, including the system default.

## System default, noisy and not forking
application/pdf; /usr/bin/zathura '%s'; test=test -n "$DISPLAY"; \
  description=Portable Document Format; nametemplate=%s.pdf
application/x-pdf; /usr/bin/zathura '%s'; test=test -n "$DISPLAY"; \
  description=Portable Document Format; nametemplate=%s.pdf

## Forks, and is quiet, but does not work when filename contains protected
## characters
application/pdf; zathura --fork '%s' >/dev/null 2>&1 ; test=test -n "$DISPLAY";\
 description=Portable Document Format; nametemplate=%s.pdf
application/x-pdf; zathura --fork '%s' >/dev/null 2>&1 ; test=test -n \
"$DISPLAY"; description=Portable Document Format; nametemplate=%s.pdf

## Works in terminal but not in mutt
application/pdf; { set -m \; /bin/mv -f -T "%s" "%s.mv" \; ( zathura "%s.mv" \
 >/dev/null 2>&1 \; /bin/rm -f "%s.mv" \; ) & } ; test=test -n "$DISPLAY"; \
description=Portable Document Format; nametemplate=%s.pdf
application/x-pdf; { set -m \; /bin/mv -f -T "%s" "%s.mv" \; ( zathura "%s.mv"\
 >/dev/null 2>&1 \; /bin/rm -f "%s.mv" \; ) & } ; test=test -n "$DISPLAY"; \
description=Portable Document Format; nametemplate=%s.pdf

I have reported this a whishlist bug against zathura in the debian bug tracking system.

1. While mutt and mc are both old programs, they are still being developed, or at least there are bugfix releases. At the time of writing, mc has been developed for almost 20 years, and there is a planned new release 4.8.11, and mutt has been around for 19 years, with the lastest release in october 2013. Compared to EMACS and the X window system, they are still very young though.

2. <rant>The whole system of MIME is a very fine idea and I use it heavily, but it is disturbing that people have come to rely on it to the extent that they tend to claim "my computer cannot open the attached file" when they really just have met an error in the MIME system (often caused by a mis-configuration, e.g. wrong Content-Type). If they would just save the attached file locally, investigate it, or at least just try to open it with a program most likely to able to handle it, they would in many cases have noticed that their "computer" actually could open the file. </rant>

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Last modified: oktober 12, 2017