Bash if string check

Question

I am evaluating following following expression. And it always evaluates to true even if CMD is START or STARTED. Am I doing something wrong?

if [ "$CMD"="START" ]; then
    echo fi
fi

tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_01.html

chown
– chown

2011-11-14 18:33:40 +00:00
Commented Nov 14, 2011 at 18:33 — chown
– chown, Commented Nov 14, 2011 at 18:33

Michael Krelin - hacker · Accepted Answer · 2011-11-14 18:22:06Z

8

Try spaces

if [ "$CMD" = "START" ] ; then
     echo fi
fi

answered Nov 14, 2011 at 18:22

Michael Krelin - hacker

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10 Comments

Michael Krelin - hacker Over a year ago

To be perfect it needs [ ] turned into [[ ]] to make sure it's evaluated by bash itself :)

Michael Krelin - hacker Over a year ago

Can you give more context, if you think it always false, then, probably, something's wrong with your $CMD.

Sirish Kumar Bethala Over a year ago

I am extracting the command string using following expression CMD=grep -i "CMD" $TPMSTATUS | cut -d":" -f2 where TPMSTATUS contains the string CMD and its value separated by :

Paul Tomblin Over a year ago

So what is in "CMD"? It probably isn't what you think. Try echo "x$CMDx" to see if you're getting spaces or something before or after.

Sirish Kumar Bethala Over a year ago

Found the problem mapping was CMD : "START", but when I remove the double quotes, it worked

|

Paul Tomblin · Accepted Answer · 2011-11-14 18:24:31Z

1

You need to have spaces around the =.

#CMD="STARTED"
#if [ "$CMD" = "START" ] ; then echo fi; fi
#CMD="START"
#if [ "$CMD" = "START" ] ; then echo fi; fi
fi
#

answered Nov 14, 2011 at 18:24

Paul Tomblin

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1 Comment

Paul Tomblin Over a year ago

@siri, then you are doing something different from what you say you're doing, because that's cut and pasted from my shell.

chown · Accepted Answer · 2011-11-14 18:37:57Z

1

From http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_07_02.html:

  [] vs. [[]]
Contrary to [, [[ prevents word splitting of variable values. So, if VAR="var with spaces", you do not need to double quote $VAR in a test - eventhough using quotes remains a good habit. Also, [[ prevents pathname expansion, so literal strings with wildcards do not try to expand to filenames. Using [[, == and != interpret strings to the right as shell glob patterns to be matched against the value to the left, for instance: [[ "value" == val* ]].

So, try:

if [[ "$CMD" == "START" ]]; then
    echo "fi"
fi

edited Nov 14, 2011 at 18:37

answered Nov 14, 2011 at 18:29

chown

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Comments

moongoal · Accepted Answer · 2011-11-14 18:27:18Z

0

You should add spaces:

if [ "$CMD" == "START" ]; then
...
fi

edited Nov 14, 2011 at 18:27

answered Nov 14, 2011 at 18:21

moongoal

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2 Comments

chown Over a year ago

-eq is for int and numer types only. Not strings.

Dan Fego Over a year ago

-eq is arithmetic, not for strings.

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