Bash bad substitution when trying to uppercase first letter

Question

I am banging my head against the wall about the Bad substitution error in Bash. Consider the following code:

getApiName() {
    IFS='-' # hyphen (-) is set as delimiter
        read -ra array <<< "$1" # str is read into an array as tokens separated by IFS
        for i in "${array[@]}"; do # access each element of array
            output+=${i^} #set first letter to uppercase
        done
    IFS=' '
    echo ${output}
}

When I do the following:

getApiName "vl-date-picker"

I get line 21: ${i^}: bad substitution

I have no clue on what's wrong. Can you guys help me please?

Thanks in advance. Regards

Answer 1

General Answer

I cannot reproduce your problem. I see two possible reasons:

• You are using a non-bash shell.
  Check this by adding the command ps to the script and look at the output. If there is no bash in the output, then you are running something different. A shebang #! /bin/bash at the beginning of your script helps to ensure that bash is used but is not a guarantee. ✱

• You have an old version of bash which does not support ${i^}
  (for instance that 20 (!) year old version pre-installed on Mac OS X).
  You can check your bash version using bash --version. ${i^} was introduced in bash 4.0, as can be read here (search for hh. There are new case-modifying word expansions) or here.

Either way, you can use a different command which should work in all Posix shells.

If you have the GNU version of sed (check with sed --version) this command could be

getApiName() {
    printf %s "$1" | sed -E 's/(^|-+)(.)/\U\2/g'
}

Nmp-Specific Answer

✱ The documentation of npm-run-script states

The actual shell your script is run within is platform dependent. By default, on Unix-like systems it is the /bin/sh command, on Windows it is the cmd.exe. The actual shell referred to by /bin/sh also depends on the system. As of [email protected] you can customize the shell with the script-shell configuration.

So to fix your problem you simply have to configure npm such that bash is used instead.

As a workaround, you could also call bash directly in your script. The simplest way to do so is a here-document:

bash -s -- "$@" <<"EOF"
    # your original script here
EOF