Unix shell script error in crontab

Question

I'm trying to schedule my shell script but when it triggered to process on a scheduled task, there is this error prompt. but when no files are to be process it just displays the echo command.

here is my code:

if [ "$(ls -A $path)" ]
    then
    for file_name in "$path"/*; do
        filebasename=$(basename "$file_name")


        prefix=${filebasename:0:4};

        if [ "$prefix" == "abcd" ] ; then

            mv  "$file_name" "$out"

        fi                          

    done


    else echo "No files available at $path"
fi

and this is the error:

SH:prefix=${filebasename:0:4}:0403-011 The specified substitution is not valid for this command

The ${var:n:m} expansion is not available in /bin/sh. You'd need to specify ksh or bash for that. Same with the == operator. — glenn jackman
– glenn jackman, Commented Dec 4, 2017 at 1:07
hi glenn thanks for this, but what should i do ? do i need to reconstruct the syntax for the code? — jcast
– jcast, Commented Dec 4, 2017 at 1:19
You also have some other syntax errors. Paste your code into shellcheck.net for further tips — glenn jackman
– glenn jackman, Commented Dec 4, 2017 at 2:08

codeforester · Accepted Answer · 2017-12-04 14:23:32Z

1

You can write your code more simply this way:

#!/bin/bash

count=0
if [[ -d "$path" ]]; then
  for file_name in "$path"/abcd*; do
    [[ -f "$file_name" ]] && { ((count++)); mv "$file_name" "$out"; }
  done
fi

if ((count == 0)); then
  echo "No files available at $path"
fi

The advantages:

No need to parse the output of ls
No need to do basename + substring for each file
Skips any directories that have a name starting with abcd

In case you are not interested in knowing whether there were matching files or not, the whole thing can be written in a single line:

find "$path" -name "abcd*" -type f -exec mv "{}" "$out" \;

edited Dec 4, 2017 at 14:23

answered Dec 4, 2017 at 1:46

codeforester

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7 Comments

ghoti Over a year ago

It's worth mentioning that the last suggestion, using find, works in any shell and does not require bash. Oh, and the cd is redundant (unless $out is relative to $path).

codeforester Over a year ago

Thanks @ghoti. I had to put in that cd because find wouldn't work without it on my Mac.

ghoti Over a year ago

That sounds strange. find in macOS should work about the same way as everywhere else. What exactly was your command, and what error did you get? Was your $out in fact relative? Might want to read about -execdir. More about your answer.. You can avoid the [[ -f ... with a shopt -s nullglob (yes, even in bash 3). And you might want to include find's -maxdepth option too, to emulate the behaviour of a bash for loop without globstar.

ghoti Over a year ago

The command depends on the values of the variables. You haven't mentioned the values of $path or $out that you tested with.

ghoti Over a year ago

On macOS, a $path of just /tmp might not have worked since that's a symlink to /private/tmp. If you set path="/tmp/" (trailing slash) it should follow the symlink rather than evaluating it as a file. Alternately, you could use the -H or -L option for find.

|

jcast · Accepted Answer · 2017-12-04 05:24:39Z

0

i use this code: prefix=$(echo ${filebasename} | cut -c1-4)

instead of prefix=${filebasename:0:4};

now it completely running in my cronjob and no error as said earlier. thanks for the help guys ! :)

answered Dec 4, 2017 at 5:24

jcast

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