multiple if condition in a bash script

grima · 03-27-2013, 11:09 AM

Hi,

I've a question concerning multiple if 'conditions' in bash.

My code looks as follows:

Code:

#!/bin/bash
for i in {1..20..1}
do

  if [[ $i -eq {7 || 11 || 18} ]]
  then
   echo "Welcome $i times"
  fi

done

For example, the 'echo' in the if condition should be for the numbers 7,
11, 18.
But it doesn't do.

Does somebody know how to do that?

Best, grima

unSpawn · 03-27-2013, 02:01 PM

Why not use a case statement: 'case $i in 7|11|18) echo "Welcome $i times";; esac;'?

colucix · 03-27-2013, 02:45 PM

Moved: This thread is more suitable in Programming and has been moved accordingly to help your thread/question get the exposure it deserves.

kooru · 03-28-2013, 03:18 AM

Hi and welcome to LQ!

Try this:

Code:

#!/bin/bash
for i in {1..20..1}
do

  if [[ $i -eq 7 || $i -eq 11 || $i -eq 18 ]]
  then
   echo "Welcome $i times"
  fi

done

David the H. · 03-28-2013, 05:09 AM

If you only need to match exact number strings, I second colucix's recommendation for a case statement. They're almost always more efficient than if tests.

Code:

#!/bin/bash
for i in {1..20}; do

    case i in
        7|11|18) echo "Welcome $i times" ;;
    esac

done

But if you need to do other numerical comparisons, then a bash "((..))" arithmetic operator is the best choice.

Code:

#!/bin/bash
for i in {1..20}; do
    if (( i == 7 || i == 11 || i >= 18 )); then
        echo "Welcome $i times"
    fi
done

When using bash or ksh, it's recommended to use [[..]] for string/file tests, and ((..)) for numerical tests. Avoid using the old [..] test unless you specifically need POSIX-style portability.

http://mywiki.wooledge.org/BashFAQ/031
http://mywiki.wooledge.org/ArithmeticExpression

And two other minor points:

1) You don't need a step operator in brace expansion if you're just counting by ones anyway.

2) Many scripters also feel that it's better to place the "do/then" keywords on the same line as the "for/while/until/if" keywords, as they are not separate commands but are paired with the opening keyword to bracket the test/input string. Putting them together on one line thus helps to better visually separate the outside block from the inside block.

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