Text snippet creator/manager in Bash

Question

Below is a script to create and manage text snippets. It is also posted on GitHub. Most of the code is error checking and displaying help because I wanted to make a solid command line interface. The blanks function is used when copying a snippet with a blank (@) character in it. The user fills in the blanks.

I am looking for a review of the script: Is it easy to use? Is the code confusing? Are there any horrible bugs that I left unnoticed?

It is tested in OS X, so I am not sure if the syntax will work elsewhere. Specifically, the pbcopy and pbpaste aliases are untested.

#!/bin/sh

list() {
    echo "snp snippets:\n"
    echo "$(ls -R $snippets_dir)"
}

move() {
    if [[ "$2" == "" && $3 == "" ]]; then
        echo "snp usage:\n"
        echo "snp move <name> <group>"
    elif [[ -e $snippets_dir/$2 ]]; then
        if -d $snippets_dir/$3 ]]; then
            mv $snippets_dir/$2 $snippets_dir/$3/$2
        else
            echo "ERROR: Group $snippets_dir/$3 does not exist."; exit 1
        fi
    else
        echo "ERROR: Snippet $2 does not exist."; exit 1
    fi
}

new() {
    if [[ "$2" == "" && "$3" == "" ]]; then
        echo "snp usage:\n"
        echo "snp new <name> \"<text>\""
        echo "snp new group <name>"
    elif [[ "$2" == "group" || "$2" == "g" ]]; then # New group
        if [[ "$3" != "" ]]; then
            mkdir $snippets_dir/$3
            echo "Created new group \"$3\"."
        else
            echo "snp usage:\n"
            echo "snp new group <name>"
        fi
    else # New snippet
        if [[ "$2" == "" ]]; then
            echo "snp usage:\n"
            echo "snp new <name> \"<text>\""
        else
            if [[ -e $snippets_dir/$2 ]]; then
                echo "Snippet $snippet_dir/$2 already exists."
                echo "Overwrite? [y/n]"
                read yn
                if [[ $yn == "y" || $yn == "Y" ]]; then
                    rm $snippets_dir/$2
                else
                    return
                fi
            fi
            printf "$3" >> $snippets_dir/$2
            echo "Created new snippet \"$2\"."
        fi
    fi
}

remove() {
    if [[ "$2" == "" ]]; then
        echo "snp usage:\n"
        echo "snp remove <name>"
        echo "snp remove group <name>"
    elif [[ "$2" == "group" || "$2" == "g" ]]; then # Remove group
        if [[ "$3" != "" ]]; then
            if [[ -e "$snippets_dir/$3" ]]; then
                rm -rf $snippets_dir/$3
                echo "Removed group \"$3\"."
            else
                echo "ERROR: Group $3 does not exist."; exit 1
            fi
        else
            echo "snp usage:\n"
            echo "snp remove group <name>"
        fi
    elif [[ "$2" != "" ]]; then # Remove snippet
        if [[ -e $snippets_dir/$2 ]]; then
            rm $snippets_dir/$2
            echo "Removed snippet \"$2\"."
        else
            echo "ERROR: Snippet $2 does not exist."; exit 1
        fi
    fi
}

blanks() {
    data=$(cat $1)
    count=0
    OIFS=$IFS
    IFS="@"
    blanx=$(echo "$data" | tr -d -c '@' | wc -c | awk '{print $1}')

    result=""

    for x in $data; do
        if [ $count -eq $blanx ]; then
            echo "$x"
            result="$result$x"
            break
        fi
        echo "$x"
        result="$result$x"
        read -p"snp> " v
        result="$result$v"
        count=`expr $count + 1`
    done
    IFS=$OIFS

    printf "$result" >> $1-tmp
}

copy() {
    if [[ "$1" == "" ]]; then
        usage
    elif [[ -e $snippets_dir/$1 ]]; then
        if [ ! $(uname -s) = "Darwin" ]; then
            alias pbcopy='xsel --clipboard --input'
        fi

        blanks $snippets_dir/$1
        cat $snippets_dir/$1-tmp | pbcopy
        echo "Snippet text copied to clipboard."

        rm $snippets_dir/$1-tmp
    else
        echo "ERROR: Snippet $1 does not exist."; exit 1
    fi
}

paste() {
    if [[ "$2" == "" ]]; then
        usage
    elif [[ -e $snippets_dir/$2 ]]; then
        if [ ! $(uname -s) = "Darwin" ]; then
            alias pbcopy='xsel --clipboard --input'
            alias pbpaste='xsel --clipboard --output'
        fi

        blanks $snippets_dir/$2
        cat $snippets_dir/$2-tmp | pbcopy
        pbpaste

        rm $snippets_dir/$2-tmp
    else
        echo "ERROR: Snippet $2 does not exist."; exit 1
    fi
}

usage() {
    echo "snp usage:\n"
    echo "snp <name>                # Copy snippet to clipboard"
    echo "snp paste <name>          # Paste name (from clipboard)"
    echo "snp new <name> \"<text>\"   # New snippet"
    echo "snp new group <name>      # New group"
    echo "snp list                  # List snippets"
    echo "snp move <name> <group>   # Move snippet to group"
    echo "snp remove <name>         # Remove snippet"
    echo "snp remove group <name>   # Remove group"
    echo "snp help                  # Display usage"
}

snippets_dir=~/".snp"

# Check for/create snippet dir
if [[ ! -d $snippets_dir ]]; then
    echo "ERROR: $snippets_dir doesn't exist."
    echo "Create it now? [y/n]"
    read yn
    if [[ $yn == "y" || $yn == "Y" ]]; then
        mkdir $snippets_dir
        echo "$snippets_dir created"
    else
        exit 0
    fi
fi

case $1 in
    p|paste)
        paste "$@" ;;
    n|new)
        new "$@" ;;
    l|list)
        list ;;
    m|move)
        move "$@" ;;
    r|remove)
        remove "$@" ;;
    h|help)
        usage ;;
    *)
        copy "$@" ;;
esac

exit 0

Answer 1

Overall

• You're using some bash-specific things ([[ ... && ... ]]), so your shebang line should be #!/bin/bash
• very good indentation, readable code
• more quotes: mv "$snippets_dir/$2" "$snippets_dir/$3/$2"

list function

• ls knows how to print to the screen, don't need echo $(ls ...)

move function

• you need echo -e if you want \n to be interpreted as a newline.
• syntax error on 2nd if, missing [[

new function

• if you use outer single quotes, don't need to escape inner double quotes (unless you need variable interpolation, of course)
• I would test for "yes" like this: if [[ ${yn,} == y* ]] -- see http://www.gnu.org/software/bash/manual/bashref.html#Shell-Parameter-Expansion

blanks function

• declare local variables with local
• to read content from a file in bash: data=$(< "$1")
• bash can do arithmetic: (( count++ )) -- see http://www.gnu.org/software/bash/manual/bashref.html#Conditional-Constructs

• you only ever use this function to copy stuff to the clipboard, so you don't need a temp file:

  blanks "$snippets_dir/$1" | pbcopy
  

• don't use printf "$astring" -- if $astring contains %-directives you'll get "not enough arguments" errors. Stick to echo, or if you're specifically avoiding a trailing newline, printf "%s" "$astring"

paste function

• I would use case here, if you decide you need OS-specific aliases:

  case $(uname -a) in
      Darwin) : ;;
      *) alias pbcopy='...'
         alias pbpaste='...'
         ;;
  esac
  

Answer 2

I am not a great fan of fall-through logic ... if there is an argument issue (missing argument, whatever), you are falling through the work functions, and letting the program end. I would make this more explicit with an exit 3. Programs should always set an exit code unless they successfully complete. I don't consider argument errors to be a successful completion.

aside - Bash has some reserved exit codes, which you should typically not use. 1 is one of the reserved exit codes. As a result, try to use values other than 1 or 2 for exit codes from shell scripts....

I would recommend creating an error-handling function... something along the lines of:

generalerror() {
    echo "snp usage:"
    echo $1
    echo
    usage
    exit 3
}

checkargument() {
    if [[ "$1" == "" ]]; then
        generalerror $2
    fi
}

This will allow you to centralize a lot of your error handling with some simpler messages/handling... the reason I am suggesting this is because of the following:

remove() {
    if [[ "$2" == "" ]]; then
        echo "snp usage:\n"
        echo "snp remove <name>"
        echo "snp remove group <name>"
    elif [[ "$2" == "group" || "$2" == "g" ]]; then # Remove group
        if [[ "$3" != "" ]]; then
            if [[ -e "$snippets_dir/$3" ]]; then
                rm -rf $snippets_dir/$3
                echo "Removed group \"$3\"."
            else
                echo "ERROR: Group $3 does not exist."; exit 1
            fi
        else
            echo "snp usage:\n"
            echo "snp remove group <name>"
        fi

That code does not exit 1.... probably because it was just an oversight... and this is why functions are good ;-)

The above code could be:

remove() {
    checkargument $2 "snp remove <name>\nsnp remove group <name>"
    if [[ "$2" == "group" || "$2" == "g" ]]; then # Remove group
        checkargument $3 "snp remove group <name>"
        ....

Right, then your error handling:

cat $snippets_dir/$1-tmp | pbcopy

The above line is critical to your program.... but, it does not check for errors.... Did the pbcopy succeed?

So:

• functions to extract common logic are useful....
• exit code set for bad values.
• different exit code for functional problems ... (failed sub-commands)
• error handling!