current community

your communities

more stack exchange communities

company blog
Stack Exchange Inbox Reputation and Badges
tour help
stack overflow careers
Sign up ×
Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute:
up vote 177 down vote favorite
36

This seems like such a simple question I'm embarrassed to ask it:

test.sh

#!/bin/bash
STR = "Hello World"
echo $STR

when I run sh test.sh I get this:

test.sh: line 2: STR: command not found

What am I doing wrong? I look at extremely basic/beginners bash scripting tutorials online and this is how they say to declare variables... So I'm not sure what I'm doing wrong.

I'm on Ubuntu Server 9.10. And yes, bash is located at /bin/bash.

share|improve this question
2  
I'm glad you did ask the question, you're not the only bash noob out there! – miller the gorilla Aug 26 at 10:40

4 Answers 4

up vote 366 down vote accepted

You cannot have spaces around your '=' sign.

When you write:

STR = "foo"

bash tries to run a command named STR with 2 arguments (the strings '=' and 'foo')

When you write:

STR =foo

bash tries to run a command named STR with 1 argument (the string '=foo')

When you write:

STR= foo

bash tries to run the command foo with STR set to the empty string in its environment.

I'm not sure if this helps to clarify or if it is mere obfuscation, but note that:

  1. the first command is exactly equivalent to: STR "=" "foo",
  2. the second is the same as STR "=foo",
  3. and the last is equivalent to STR="" foo.

The relevant section of the sh language spec, section 2.9.1 states:

A "simple command" is a sequence of optional variable assignments and redirections, in any sequence, optionally followed by words and redirections, terminated by a control operator.

In that context, a word is the command that bash is going to run. Any string containing = (in any position other than at the beginning of the string) which is not a redirection is a variable assignment, while any string that is not a redirection and does not contain = is a command. In STR = "foo", STR is not a variable assignment.

share|improve this answer
32  
+1 for demonstrating what happens with all possible types of spacing around the equals sign. – chepner Jun 18 '12 at 17:58
4  
Why I can't favorite answers on SO? :) – hek2mgl Mar 19 '14 at 23:58
up vote 65 down vote

Drop the spaces around the = sign:

#!/bin/bash 
STR="Hello World" 
echo $STR
share|improve this answer
5  
This is funny, though, as set foo = bar is a common mistake in Windows batch files as well—and there the batch language is ridiculed for it ;-) – Joey Feb 15 '10 at 18:36
    
Thanks @joey. I was stuck in writing a shell script where i was initializing variables with spaces after "=". You saved my day – Lalit Rao Oct 2 at 13:10
up vote 2 down vote

In the interactive mode ! everything looks fine

:~$ str="Hello World"

:~$ echo $str

Hello World

Obviously ! as Johannes said, no space around '='. In case there is any space around '=' then in the interactive mode it gives errors as `

No command 'str' found

share|improve this answer
up vote 1 down vote

I have read all answers, but there is still one thing to note:

STR= hello

STR=hello ls

The 1st line will run command "hello", but will NOT set STR to "".

The 2nd line will run command "ls" but will NOT set STR to "hello".

Let use echo $STR for each step to see the result.

share|improve this answer
2  
Not strictly true. The first command does not modify the value of STR in the current shell, but it does set it (to the empty string) in the environment of hello. Similarly, the second command does set STR (to the string 'hello') in the environment of ls. (But ls ignores the value.) – William Pursell Apr 9 at 21:00

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.