Author: Jake Alheid

Make MacVim’s mvim script use tabs and play nice with the command line

Jake Alheid 9 Comments

tl;dr: Replace the mvim script with this modified version: https://gist.github.com/3780676

MacVim comes with a really sweet script called mvim, which lets you launch MacVim and edit files from the command line. Unfortunately, this script is a little weak in a few ways:

  • It doesn’t let you edit multiple files.
  • It doesn’t let you pass in command line options.
  • It doesn’t let you use new tabs for opening new files into an existing window.
  • It doesn’t let you pipe stdin into vim for viewing (great with diffs).

All those things are awesome, so let’s make the mvim script better! How do we do that?

Well, first we add some extra command line options parsing to detect if we’re in diff mode, if we’re using stdin, and to preserve options for passing back into MacVim later. At Line 60 we add the following:

# Add new flags for different modes
stdin=false
diffmode=false
# Preserve command line options lazily
while [ -n "$1" ]; do
  case $1 in 
  -d) diffmode=true; shift;;
  -?*) opts="$opts $1"; shift;;
  -) stdin=true; break;;
  *) echo "*"; break;; 
  esac
done

This is a pretty normal bash argument getting loop. We look for -d (diff mode) and – (stdin) separate from other arguments. We also need to modify the command that starts MacVim to handle our different modes, etc. So we replace that command (originally on line 69):

# Last step:  fire up vim.
# The program should fork by default when started in GUI mode, but it does
# not; we work around this when this script is invoked as "gvim" or "rgview"
# etc., but not when it is invoked as "vim -g".
if [ "$gui" ]; then
	# Note: this isn't perfect, because any error output goes to the
	# terminal instead of the console log.
	# But if you use open instead, you will need to fully qualify the
	# path names for any filenames you specify, which is hard.
	exec "$binary" -g $opts ${1:+"$@"}
else
	exec "$binary" $opts ${1:+"$@"}
fi

With this better command:

# Last step:  fire up vim.
# The program should fork by default when started in GUI mode, but it does
# not; we work around this when this script is invoked as "gvim" or "rgview"
# etc., but not when it is invoked as "vim -g".
if [ "$gui" ]; then
  # Note: this isn't perfect, because any error output goes to the
  # terminal instead of the console log.
  # But if you use open instead, you will need to fully qualify the
  # path names for any filenames you specify, which is hard.

  # Handle stdin
  if $stdin; then
    exec "$binary" -g $opts -
  elif $diffmode; then
    exec "$binary" -f -g -d $opts $*
  elif $tabs && [[ `$binary --serverlist` = "VIM" ]]; then
    #make macvim open stuff in the same window instead of new ones
    exec "$binary" -g $opts --remote-tab-silent ${1:+"$@"} & 
    wait
  else
    exec "$binary" -g $opts ${1:+"$@"}
  fi
else
  exec "$binary" $opts ${1:+"$@"}
fi

The first two branches are pretty clear – they just invoke the MacVim binary in the correct way, for our different modes. The third one uses the very awesome –remote-tab-silent option, which gives us the ability to reuse the same window with new tabs when we edit multiple files. Neato!

Finally, if you don’t want to do the modifications yourself, it’s available as a gist, so you can download it and use it as a drop-in replacement for the vanilla mvim script: https://gist.github.com/3780676

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Building a Better Bash Script

Jake Alheid 13 Comments

I often find myself writing a lot of bash scripts that wrap functionality of my services and programs in ways that make my job easier. While bash doesn’t lend itself well to traditional “inheriting” of program elements, it still is very helpful to build a toolbox of snippets, templates, and bits of script that let me assemble new scripts with tried and true methods to get things done.

One of the hardest things to do well in bash is parsing command line options in a consistent cross platform way. The template below shows an example of how to do this that allows for short, long and positional options.

The template uses getopt to normalize short options after parsing long options in a two pass approach. Using getopt transforms options into their canonical form – for example, the option string “-c foobar -laht -v” after being parsed by getopt, becomes “-c foobar -l -a -h -t -v”, allowing them to be handled more consistently.

The getopt string (stored in the variable “opts” below) consists of all the short option letters, with letters that take an argument (e.g. cmd -a foo) being followed by a colon. So if I had short options “a” and “b”, and “b” took an argument, my getopt string would be “ab:”.

# Option defaults
OPT="value"

# Gets the command name without path
cmd(){ echo `basename $0`; }

# Help command output
usage(){
echo "\
`cmd` [OPTION...]
-f, --flag; Set a flag
-o, --opt; Set an option with argument (default: $OPT)
-v, --verbose; Enable verbose output (include multiple times for more
             ; verbosity, e.g. -vvv)
" | column -t -s ";"
}

# Error message
error(){
    echo "`cmd`: invalid option -- '$1'";
    echo "Try '`cmd` -h' for more information.";
    exit 1;
}

# getopt string
opts="fvo:"

# There's two passes here. The first pass handles the long options and
# any short option that is already in canonical form. The second pass
# uses `getopt` to canonicalize any remaining short options and handle
# them
for pass in 1 2; do
    while [ -n "$1" ]; do
        case $1 in
            --) shift; break;;
            -*) case $1 in
                -f|--flag)     FLAG=1;;
                -o|--opt)      OPT=$2; shift;;
                -v|--verbose)  VERBOSE=$(($VERBOSE + 1));;
                --*)           error $1;;
                -*)            if [ $pass -eq 1 ]; then ARGS="$ARGS $1";
                               else error $1; fi;;
                esac;;
            *)  if [ $pass -eq 1 ]; then ARGS="$ARGS $1";
                else error $1; fi;;
        esac
        shift
    done
    if [ $pass -eq 1 ]; then ARGS=`getopt $opts $ARGS`
        if [ $? != 0 ]; then usage; exit 2; fi; set -- $ARGS
    fi
done

# Handle positional arguments
if [ -n "$*" ]; then
    echo "`cmd`: Extra arguments -- $*"
    echo "Try '`cmd` -h' for more information."
    exit 1
fi

# Set verbosity
if [ "0$VERBOSE" -eq 0 ]; then
    # Default, quiet
elif [ $VERBOSE -eq 1 ]; then
    # Enable log messages
elif [ $VERBOSE -ge 2 ]; then
    # Enable high verbosity
elif [ $VERBOSE -ge 3 ]; then
    # Enable debug verbosity
fi

The other interesting thing is that this template allows for multiple verbose flags (-v, -vv, -vvv, etc.) to specify different levels of verbosity – which can be a very handy thing for debugging a misbehaving script or controlling output from a subcommand.

Have other good tips for bash scripting? Share them in the comments!

View this template as a gist on github: https://gist.github.com/2765260

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