Question

Bash scripting does my head in. I have searched for regex assignment, but not really finding answers I understand.

I have files in a directory. I need to loop through the files and check if they fit certain criteria. File names under a certain sequence need to have their sequence increased. Those over a certain sequence need to trigger an alert.

I have pseudo code and need help turning it into correct bash syntax:

#!/bin/sh

function check_file()
{
    # example file name "LOG_20101031144515_001.csv"
    filename=$1

    # attempt to get the sequence (ex. 001) part of file

    # if sequence is greater than 003, then raise alert

    # else change file name to next sequence (ex. LOG_20101031144515_002.csv)
}

for i in `ls -Ar`; do check_file $i; done;

If PHP were an option, I could do the following:

function check_file($file){
    //example file 'LOG_20101031144515_001.csv';

    $parts = explode('.',$file);
    preg_match('/\d{3}$/', $parts[0], $matches);
    if ($matches){
        $sequence = $matches[0];
        $seq      = intval($sequence);

        if ($seq > 3){
            // do some code to fire alert (ex. email webmaster)
        }
        else{
            // rename file with new sequence
            $new_seq  = sprintf('%03d', ++$seq);
            $new_file = str_replace("_$sequence", "_$new_seq", $file);
            rename($file, $new_file);
        }
    }
}

So long story short, I’m hoping someone can help port the PHP check_file function to the bash equivalent.

Thank you

Answer 1

First of all, your question is tagged [bash], but your shebang is #!/bin/sh. I’m going to assume Bash.

#!/bin/bash
function check_file()
{
    # example file name "LOG_20101031144515_001.csv"
    filename=$1

    # attempt to get the sequence (ex. 001) part of file

    seq=${filename%.csv}
    seq=${seq##*_}

    # if sequence is greater than 003, then raise alert

    if (( 10#$seq > 3 ))
    then
        echo "Alert!"
    else
        # else change file name to next sequence (ex. LOG_20101031144515_002.csv)
        printf -v newseq "%03d" $((seq + 1))
        echo "${filename/$seq/$newseq}" # or you could set a variable or do a mv
    fi
}