command line argument in bash gives an error

Question

I want to write a bash script and one of the command line arguments is a string like A:

sh bash.sh file.in A

The script contains:

format=$2

if [$format = "A"]; then 
    ...
else 
    ...
fi

As a result I get this error:

bash.sh: line 20: [A: command not found

sat · Answer 1 · 2014-03-18T05:33:51.393

3

Try this:

#!/bin/bash

format="$2"

if [ "$format" = "A" ];then
   echo "Equal";
else
   echo "Not equal";
fi

(OR)

if [[ $format = "A" ]];then
    ...
else
    ...
fi

edited Mar 18 '14 at 05:33

answered Mar 17 '14 at 12:36

sat

Use `=` instead of `==`. If `==` works, so would the superior `if [[ "$format" == "A" ]]; then`. – chepner Mar 17 '14 at 12:43
a little explanation with the answer is always welcome – UmNyobe Mar 17 '14 at 12:45

awiseman · Accepted Answer · 2014-03-17T14:44:29.973

3

POSIX shell syntax requires a space between the [ ] brackets and the expression.

Try this:

if [ "$format" = "A" ]; then

...

else

...

fi

Also, if portability isn't a concern, you can use the more robust

[[ "$format" == "A" ]]

edited Mar 17 '14 at 14:44

answered Mar 17 '14 at 12:39

awiseman

2

`=` is not an assignment operator in a `test`/`[` command. `==` is only accepted by `bash`, and is arguably a bug to do so. – chepner Mar 17 '14 at 12:42
Thanks for the correction. I've edited the incorrect part out. Not sure I like the ambiguity of having an operator mean different things in different contexts... but I'll read up some more on it. – awiseman Mar 17 '14 at 12:47
1

Since the question is tagged as `bash` shouldn't the expression be `[[ "$format" == "A" ]]`? See https://stackoverflow.com/questions/669452/is-preferable-over-in-bash-scripts – Saucier Mar 17 '14 at 12:49
There, how's that for a compromise? :) I've been trying to not presume too much when giving answers and I try to default to as close to the as-posted question as will work. This at least proposes an alternate option. – awiseman Mar 17 '14 at 13:10
1

It's not just bash that requires the space, it's the POSIX shell syntax that requires a space between any command and its arguments. Don't forget that `[` is a (possibly builtin) command. – glenn jackman Mar 17 '14 at 14:40
Hopefully, you guys are getting rep for this. This answer has become a team effort :) – awiseman Mar 17 '14 at 14:45

2 Answers2