Bash Processing of Command Line Parameters that Include Spaces

Internal

• bash

Overview

This page documents a shell coding pattern to be used when some of the command line parameters need to be processed in the wrapper shell script, and the rest of the parameters, some of which may include spaces, are passed unchanged to the target process. The pattern uses a special separator character, that is injected between the arguments to be forwarded to the lower layer, followed by the recreation of the command line with set.

The pattern handles consistently both double-quote enclosed and single-quote encloses command line arguments that contain spaces.

# ...

local args
local separator=$'\x1f' # US - unit separator

while [ -n "$1" ]; do

    if [ "$1" = "..." ]; then

        #
        # process arguments that make sense at this layer
        #
        echo "processing $1 at this level ..."

        # ...

    else

        #
        # ... and accumulate the rest of the arguments, separated by the special separator character
        #
        [ -z "${args}" ] && args="$1" || args="${args}${separator}$1"
    fi
    shift
done

#
# re-assemble the command line, by re-initializing the positional parameters, and pass it to the underlying process
#
IFS=${separator}
set - ${args}
IFS="$(printf ' \t\n')" # restore the standard separators

#
# Use "$@" built-in variable, which encloses each positional parameter in its own set of double quotes
#

java -cp ... io.novaordis.playground.Main "$@"

Note that the command can be debugged as follows:

...

local command_prefix="java -cp ... io.novaordis.playground.Main" 
debug ${command_prefix} "$@"
${command_prefix} "$@"