IF condition throwing error in Unix Command Prompt

Question

Below is my simple if command which throws command not found but any it prints else part value...

-bash-3.00$ if ["$a"="10"]; then echo "hello"; else echo "hi"; fi;

output:

-bash: [10=10]: command not found
hi

Can any one please let me know what is the problem ?

Friendly reminder that there are automated linting and analysis tools for these things. — that other guy
– that other guy, Commented Oct 25, 2013 at 18:06

falsetru · Accepted Answer · 2013-10-25 06:20:47Z

3

Add spaces between [/] and predicate expression:

if [ "$a" = "10" ]; then echo "hello"; else echo "hi"; fi;
#   ^           ^

[ is a program:

$ which [
/usr/bin/[

Without space, [10=10] is recognized as a program name and is executed instead of [.

$ a=10
$ if [ "$a" = "10" ]; then echo "hello"; else echo "hi"; fi;
hello
$ a=20
$ if [ "$a" = "10" ]; then echo "hello"; else echo "hi"; fi;
hi

edited Oct 25, 2013 at 6:20

answered Oct 25, 2013 at 6:13

falsetru

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5 Comments

Priyatham51 Over a year ago

I thought he also need to use -eq instead = . Is that right ?

SheetJS Over a year ago

@Priyatham51 since both arguments are quoted, = is fine

that other guy Over a year ago

@KeithThompson It's actually the other way around. -eq is for numbers and = is for strings.

Keith Thompson Over a year ago

@thatotherguy: Yeah, I knew that (fumble fingers). I'll delete my previous comment and post a corrected version.

Keith Thompson Over a year ago

@Priyatham51: (Correcting my previous comment) -eq is for numeric comparisons. = is for string comparisons. man test or info coreutils test for details. Or info bash and look under "Bourne shell builtins" for test.

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