How can I check if and greater than condition in linux?

Question

If tag_len is greater than 18 or tag_len is 19 and the tag is not ends with "A", I want to cut the tag to length 18.

I tried several options but that is not working correctly. Could you let me now how I can do this?

#officail daily release TAG check

official_tag_len=18

export tag_len=`expr length $TAG`

if (($tag_len > $official_tag_len))

then

    echo "$TAG length is greater than $official_tag_len"
    if (($tag_len == ($official_tag_len+1))) && (($TAG == *A))
    then
        echo $TAG is an AM daily tag
    else
        echo $TAG is a temporary tag. reset to daily tag
        export TAG=$($TAG:0:$official_tag_len)
    fi
fi

UPDATE

the final error message is

e7e10_preqe2:0:18: command not found

I edit the code "export TAG=$($TAG:0:$official_tag_len)" referring to Extract substring in Bash

and one more thing, at first I wrote [[ instead of (( in if condition but command not found error occurs in [[ line.

Usually, I used [ ] expression in if condition. Are there any exceptional cases?

What is the error that you get? If you aren't getting an error, what is the output you get and what were you expecting it to be? — Taryn East, Feb 28 '14 at 00:21
1. export TAG=$($TAG:0:$official_tag_len) command not found error occurs — 500004dolkong, Feb 28 '14 at 00:23
Check out [Gregs Wiki](http://mywiki.wooledge.org/BashGuide/TestsAndConditionals#Conditional_Blocks_.28if.2C_test_and_.5B.5B.29) for more info on conditionals work in bash. — w0ng, Feb 28 '14 at 00:24
He - please edit your questions and add your output and errors to your question :) — Taryn East, Feb 28 '14 at 00:25
Also - I don't understand what you mean about the `[[` - can you edit your question and give that as a full example? — Taryn East, Feb 28 '14 at 00:26

score 1 · Accepted Answer · answered Feb 28 '14 at 01:05

The question setup is a bit difficult to understand, but I think this runs the way you want on bash. You didn't specify interpreter for the question..

I have taken liberty to take the "TAG" as input parameter (TAG=$1, and calculate it's length using command wc).

I have replaced all the if statements to use square brackets, and also use keyword -gt (greater than) for comparison (use lt for <, and eq for ==). These are meant to be used for numerical comparison.

#!/bin/bash

#officail daily release TAG check

TAG=$1
tag_len=`echo $TAG | wc -c`

official_tag_len=18

echo "input $tag, length: $tag_len"

if [[ $tag_len -gt $official_tag_len ]];
then

  echo "$TAG length is greater than $official_tag_len"
  if [[ $tag_len -eq $(($official_tag_len+1)) ]] && [[ $TAG == *A ]];
  then
    echo $TAG is an AM daily tag
  else
    echo $TAG is a temporary tag. reset to daily tag
    export TAG=${TAG:0:official_tag_len}
    echo "new tag: [$TAG]"
  fi
fi

I'm sorry for my uncertain codes and questions. But your answer includes all information exactly I wonder. Thanks alot. — 500004dolkong, Feb 28 '14 at 01:58

How can I check if and greater than condition in linux?

1 Answers1