using if and a boolean function in bash script: if condition evaluates to false when function returns true

Question

is_dir_empty(){

    for file in "$1"
    do
        if [ "$file" != "$1" ]; then
            return 0
        fi
    done
    echo "return 1"
    return 1
}

file="/home/tmp/*.sh"

if is_dir_empty "$file"; then
    echo "empty"
else echo "not empty"
fi

it outputs

return 1
not empty

so is_dir_empty returned 1 but if condition evaluated to false somehow.... why?

Possible duplicate of bash functions: return boolean to be used in if — Mad Physicist
– Mad Physicist, Commented Feb 1, 2016 at 19:09

Michael Day · Accepted Answer · 2013-02-05 01:47:33Z

9

Because shell scripts follow the Unix convention of expecting utilities to return zero for success and non-zero for failure, so boolean conditions are inverted.

answered Feb 5, 2013 at 1:47

Michael Day

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Comments

that other guy · Accepted Answer · 2017-10-23 16:36:38Z

2

Globs are not expanded in double quotes, so you're always comparing against the literal value /home/tmp/*.sh. Unquote $1 in the for loop, and it'll word split and glob expand into a list of .sh files (this online tool would have pointed this out automatically).

Also, unlike in C, zero is considered success and non-zero failure.

edited Oct 23, 2017 at 16:36

answered Feb 5, 2013 at 1:53

that other guy

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2 Comments

Stuart Axon Over a year ago

The online tool looks like it would have been useful, is there an equivalent that is up today?

that other guy Over a year ago

@StuartAxon Today there's ShellCheck. It has an online version and can also be installed locally

Hamid Reza Moradi · Accepted Answer · 2013-02-05 07:18:02Z

0

you can check if a directory is empty by:

[ "$(ls -A /path/to/directory)" ] && echo "Not Empty" || echo "Empty"

answered Feb 5, 2013 at 7:18

Hamid Reza Moradi

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