shell script: integer expression expected

Question

#!/bin/bash
if [$# -ne 1];
then
  echo "/root/script.sh a|b"
else if [$1 ='a'];
then
  echo "b"
else if [$1 ='b']; then
  echo "a"
else 
  echo "/root/script.sh a|b"
fi

I'm getting below error while run above script in Linux.

bar.sh: line 2: [: S#: integer expression expected
a

Could you please help to remove this error?

Gee, I do hope you are not practicing your shell scripting in the root account. — zwol
– zwol, Commented Jul 22, 2012 at 18:35
The S# in the error message looks like you misspelled $# either when transcribing the error message or in the code. — tripleee
– tripleee, Commented Jul 22, 2012 at 19:03

Rayne · Accepted Answer · 2012-07-22 18:26:58Z

5

if [$# -ne 1];

[ and ] requires spacing. Example:

if [ $# -ne 1 ];

And else if should be elif

#!/bin/bash
if [ "$#" -ne 1 ];
then
  echo "/root/script.sh a|b"
elif [ "$1" ='a' ];
then
  echo "b"
elif [ "$1" ='b' ]; then
  echo "a"
else
  echo "/root/script.sh a|b"
fi

Do not forget to quote variables. It is not every time necessary, but recommended.

Question: Why do i have -1?

edited Jul 22, 2012 at 18:26

answered Jul 22, 2012 at 18:20

Rayne

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4 Comments

zwol Over a year ago

The semicolons after the ]s are only necessary if you put the then on the same line.

Rayne Over a year ago

I know, but this is no problem so i did not change it.

zwol Over a year ago

Doh! I didn't notice that that was how it was in the original script.

Gordon Davisson Over a year ago

You also need spaces around the operators (including after the =) inside [ ... ]

chrisaycock · Accepted Answer · 2012-07-22 18:26:45Z

2

Bash doesn't allow else if. Instead, use elif.

Also, you need spacing within your [...] expression.

#!/bin/bash
if [ $# -ne 1 ];
then
  echo "/root/script.sh a|b"
elif [ $1 ='a' ];
then
  echo "b"
elif [ $1 ='b' ]; then
  echo "a"
else 
  echo "/root/script.sh a|b"
fi

answered Jul 22, 2012 at 18:26

chrisaycock

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