Command not found error in Bash variable assignment

600
votes

I have this script called 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.

5
bashshellsyntaxshvariable-assignment
I'm glad you did ask the question, you're not the only bash noob out there! – miller the gorilla
Thanks for asking that question. This is not a question to be embarrassed about. I am working late night in office & there is no Bash expert around me to answer this. – Adway Lele
These days (almost seven years later!) there's a FOSS linter/analyzer called shellcheck that will autodetect this and other common syntax issues. It can be used online or installed offline and integrated in your editor. – that other guy
See also stackoverflow.com/questions/26971987/… – tripleee
I'd recommend you to use: #!/usr/bin/env bash instead of putting directly #!/bin/bash unless you're absolutely sure your bash is in /bin because of this answer: stackoverflow.com/a/21613044/3589567 – Alejandro Blasco

5 Answers

1056
votes

You cannot have spaces around the = 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 and in which the portion of the string before the = is a valid variable name is a variable assignment, while any string that is not a redirection or a variable assignment is a command. In STR = "foo", STR is not a variable assignment.

175
votes

Drop the spaces around the = sign:

#!/bin/bash 
STR="Hello World" 
echo $STR
8
votes

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

7
votes

I know this has been answered with a very high-quality answer. But, in short, you cant have spaces.

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

Didn't work because of the spaces around the equal sign. If you were to run...

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

It would work

4
votes

When you define any variable then you do not have to put in any extra spaces.

E.g.

name = "Stack Overflow"  
// it is not valid, you will get an error saying- "Command not found"

So remove spaces:

name="Stack Overflow"

and it will work fine.