Bash string concatenation asking for numeric argument

Question

I need a bash function that prefixes a date_time string with a string.

show_neb_2017_05_20_16_55

My current function I am hoping would have done this, except that it is requiring a numeric argument.

    function show_neb() {
        a='show_neb_'$(date +"%Y_%m_%d__%H_%M")
        return $a
        }

    echo $(show_neb)

I would have expected it to work, but it isn't. Isn't this just a direct standard output to a string?

The point you are missing is return only returns success/failure, not a string. to do what you were attempting, try echo "$a"; return 0; — David C. Rankin
– David C. Rankin, Commented Jun 14, 2017 at 19:20

chepner · Accepted Answer · 2017-06-14 19:59:00Z

2

return can only be used to provide an integer exit code for the function, not an arbitrary string value. To simulate a return value, you need to write to standard output, then capture that via a command substitution.

show_neb () {
    date +"show_neb_%Y_%m_%d__%H_%M"
    # Replacing echo "show_neb_$(date +"%Y_%m_%d__%H_%M")"
}

val=$(show_neb)

Shell functions really aren't functions in the usual sense; they are more like in-memory shell scripts that are sourced.

edited Jun 14, 2017 at 19:59

answered Jun 14, 2017 at 19:17

chepner

538k77 gold badges595 silver badges747 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

123 Over a year ago

Just running the function would do what they want.

chepner Over a year ago

Yes; I'm emphasizing what you would need if you want to assign the "return value" to a variable.

David C. Rankin Over a year ago

Making good use of the date output within the function rather than an explicit echo or printf :) (of course in this case, you can get rid of the show_neb function altogether and just use command substitution on the date command itself)

Collectives™ on Stack Overflow

Bash string concatenation asking for numeric argument

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related