Reading quoted/escaped arguments correctly from a string

Question

I\'m encountering an issue passing an argument to a command in a Bash script.

poc.sh:

#!/bin/bash

ARGS=\'\"hi there\" test\'
./swap ${ARGS}
<         


        

Answer 1

Ugly Idea Alert: Pure Bash Function

Here's a quoted-string parser written in pure bash (what terrible fun)!

Caveat: just like the xargs example above, this errors in the case of an escaped quote. This could be fixed... but much better to do in an actual programming language.

Example Usage

MY_ARGS="foo 'bar baz' qux * "'$(dangerous)'" sudo ls -lah"

# Create array from multi-line string
IFS=$'\r\n' GLOBIGNORE='*' args=($(parseargs "$MY_ARGS"))

# Show each of the arguments array
for arg in "${args[@]}"; do
    echo "$arg"
done

Example Output

foo
bar baz
qux
*

Parse Argument Function

This literally goes character-by-character and either adds to the current string or the current array.

set -u
set -e

# ParseArgs will parse a string that contains quoted strings the same as bash does
# (same as most other *nix shells do). This is secure in the sense that it doesn't do any
# executing or interpreting. However, it also doesn't do any escaping, so you shouldn't pass
# these strings to shells without escaping them.
parseargs() {
    notquote="-"
    str=$1
    declare -a args=()
    s=""

    # Strip leading space, then trailing space, then end with space.
    str="${str## }"
    str="${str%% }"
    str+=" "

    last_quote="${notquote}"
    is_space=""
    n=$(( ${#str} - 1 ))

    for ((i=0;i<=$n;i+=1)); do
        c="${str:$i:1}"

        # If we're ending a quote, break out and skip this character
        if [ "$c" == "$last_quote" ]; then
            last_quote=$notquote
            continue
        fi

        # If we're in a quote, count this character
        if [ "$last_quote" != "$notquote" ]; then
            s+=$c
            continue
        fi

        # If we encounter a quote, enter it and skip this character
        if [ "$c" == "'" ] || [ "$c" == '"' ]; then
            is_space=""
            last_quote=$c
            continue
        fi

        # If it's a space, store the string
        re="[[:space:]]+" # must be used as a var, not a literal
        if [[ $c =~ $re ]]; then
            if [ "0" == "$i" ] || [ -n "$is_space" ]; then
                echo continue $i $is_space
                continue
            fi
            is_space="true"
            args+=("$s")
            s=""
            continue
        fi

        is_space=""
        s+="$c"
    done

    if [ "$last_quote" != "$notquote" ]; then
        >&2 echo "error: quote not terminated"
        return 1
    fi

    for arg in "${args[@]}"; do
        echo "$arg"
    done
    return 0
}

I may or may not keep this updated at:

• https://git.coolaj86.com/coolaj86/git-scripts/src/branch/master/git-proxy

Seems like a rather stupid thing to do... but I had the itch... oh well.