Shell script: use while loop to check string contents using [ ]

Question

I am trying to check a string that is output from a program, if the string matches a certain content, the while-loop will stop the program. At the same time, I need to count how many times the program has run:

x = "Lookup success"  # this is supposed to be the output from the program
INTERVAL=0  # count the number of runs

while ["$x" != "Lookup failed"]   # only break out the while loop when "Lookup failed" happened in the program
do
   echo "not failed"     # do something
   $x = "Lookup failed"     # just for testing the break-out
   INTERVAL=(( $INTERVAL + 10 )); # the interval increments by 10  
done

echo $x
echo $INTERVAL

But this shell script is not working, with this error:

./test.sh: line 9: x: command not found 
./test.sh: line 12: [[: command not found

Could someone help me please? I appreciate your help.

Kindly accept or upvote the answers if it helped you.

Anubhab
– Anubhab

2013-12-09 06:37:46 +00:00
Commented Dec 9, 2013 at 6:37 — Anubhab
– Anubhab, Commented Dec 9, 2013 at 6:37

Jonathan Leffler · Accepted Answer · 2013-12-09 06:17:36Z

4

You need spaces around the [ command name. You also need a space before the ] argument at the end of the command.

You also cannot have spaces around assignments in shell. And your assignment in the loop does not need a $ at the start.

x="Lookup success"
INTERVAL=0  # count the number of runs

while [ "$x" != "Lookup failed" ]
do
    echo "not failed"
    x="Lookup failed"
    INTERVAL=(( $INTERVAL + 10 ))  
done

echo $x
echo $INTERVAL

answered Dec 9, 2013 at 6:17

Jonathan Leffler

759k145 gold badges961 silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

maverick · Accepted Answer · 2013-12-09 08:32:28Z

3

Not sure if there's a shell that would accept INTERVAL=((...)); my version of ksh and bash on two platforms does not. INTERVAL=$((...)) does work:

#!/bin/bash

x="Lookup success"
INTERVAL=0  # count the number of runs

while [ "$x" != "Lookup failed" ]
do
    echo "not failed"
    x="Lookup failed"
    INTERVAL=$(( $INTERVAL + 10 ))  
done

echo $x
echo $INTERVAL

Credits go to @JonathanLeffler. I'll appreciate up-votes so that next time I don't have to copy-paste others' solution for pointing out a simple typo (comment rights start with rep>=50).

answered Dec 9, 2013 at 8:32

maverick

4362 silver badges10 bronze badges

Comments

Jonathan Leffler · Accepted Answer · 2013-12-09 06:20:35Z

2

Add a space after [ and before ].

Also, as Jonathan said, you cannot have space in assignments as well.

edited Dec 9, 2013 at 6:20

Jonathan Leffler

759k145 gold badges961 silver badges1.3k bronze badges

answered Dec 9, 2013 at 6:17

Anubhab

1,7862 gold badges18 silver badges28 bronze badges

Collectives™ on Stack Overflow

Shell script: use while loop to check string contents using [ ]

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related