.bash_subshell

# some subshell-related tricks and aliases

# prepend the string in param2+ to the file provided in param1
# if param1 does not already exist, it will be created
# if param2+ is not provided, stdin will be prepended instead
# 
# if your file is large, use a temporary file instead of prepend
# since prepend must load your entire file into memory
# 
# ex1: prepend file "prepend me"
# ex2: echo -ne "prepend\tmore\tcolumn\tnames" | prepend file.tsv
# ex3: run the command "prepend file", type the text you want prepended, and then press Ctrl+D
# ex4: mkfifo temp && echo " any type of file!" > temp & prepend temp -n "it should work with" & sleep 1 && cat temp && rm temp
prepend() {
    touch "$1" 2>/dev/null || {
        echo "file is invalid" 1>&2; return 1
    }
    f="$1"
    shift
    if [ "$#" -eq 0 ]; then
        echo "$(cat - "$f")" > "$f"
    else
        echo "$(echo "$@" | cat - "$f")" > "$f"
    fi
}