Command not found error in Bash variable assignment

Question

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.

I'm glad you did ask the question, you're not the only bash noob out there! — miller the gorilla, Commented Aug 26, 2015 at 10:40
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, Commented Jan 19, 2016 at 16:49
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, Commented Nov 8, 2016 at 17:52
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 — wchmb, Commented Feb 21, 2018 at 10:58

William Pursell · Accepted Answer · 2021-01-29 13:15:59Z

1257

+100

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:

the first command is exactly equivalent to: STR "=" "foo",
the second is the same as STR "=foo",
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.

edited Jan 29, 2021 at 13:15

answered Feb 15, 2010 at 18:34

William Pursell

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11

If you have a variable with a name that contaings "-", the same error happens. In that case, the solution is to remove the "-"
– chomp
Commented Jun 17, 2016 at 2:27
3

chomp@ In rule 7b of section 2.10.10 of pubs.opengroup.org/onlinepubs/9699919799 "If all the characters preceding '=' form a valid name (see XBD Name), the token ASSIGNMENT_WORD shall be returned." Following the link to section 3.231 of pubs.opengroup.org/onlinepubs/9699919799, we find "In the shell command language, a word consisting solely of underscores, digits, and alphabetics from the portable character set. The first character of a name is not a digit.". So the word FOO-BAR=qux is not a variable assignment since FOO-BAR is not a valid name.
– William Pursell
Commented Jun 17, 2016 at 13:30
2

I am offering a bounty to reward this clear explanation to an always common issue for beginners (well, and also to be able to find it faster whenever I want to link it :D). Thanks for making things this easy!
– fedorqui
Commented Aug 16, 2016 at 11:54
1

@fedorqui Thanks! I'm not entirely convinced that this is a clear explanation, and I often wonder if it could be made simpler.
– William Pursell
Commented Aug 16, 2016 at 21:29
2

@Timo $st=$i is not a variable assignment. It expands to a string, and that string is executed as a command. It seems like you are trying to do eval $st=$i. Don't do that.
– William Pursell
Commented Nov 9, 2020 at 17:05

| Show 5 more comments

Joey · Accepted Answer · 2010-02-15 18:34:40Z

207

Drop the spaces around the = sign:

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

answered Feb 15, 2010 at 18:34

Joey

355k87 gold badges701 silver badges696 bronze badges

12

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
Commented Feb 15, 2010 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
Commented Oct 2, 2015 at 13:10
Why bash doesn't accept numbers in the left field? like 3="Hello World", it complains about command not found
– Freedo
Commented Jan 19, 2018 at 16:51
in a while, fails for me: eval $tag_found=0
– Kiquenet
Commented Aug 14, 2024 at 8:29

Add a comment |

Benjamin W. · Accepted Answer · 2020-05-17 02:35:39Z

11

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

edited May 17, 2020 at 2:35

Benjamin W.

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answered Feb 26, 2010 at 6:33

Arkapravo

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3

But note the OP was saying STR = "Hello World", so this answer does not apply here.
– fedorqui
Commented Aug 16, 2016 at 12:05
@Arkapravo what is the meaning of the interactive mode, is it has something to do with the $ mark
– Kasun Siyambalapitiya
Commented Nov 22, 2016 at 13:24
@KasunSiyambalapitiya by "interactive mode" he means typing those commands in the actual terminal, not into a script.
– numbermaniac
Commented Jan 5, 2017 at 23:59

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Derek Haber · Accepted Answer · 2019-03-27 12:58:52Z

9

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

answered Mar 27, 2019 at 12:58

Derek Haber

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Knowledge Cube · Accepted Answer · 2017-06-19 16:42:45Z

5

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.

edited Jun 19, 2017 at 16:42

Knowledge Cube

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answered Jun 19, 2017 at 15:16

Ravi Solanki

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Zhenya · Accepted Answer · 2023-10-20 00:42:27Z

1

To add to the accepted answer - using dashes in your variable name will give the same error. Remove - to get rid of the error.

STR-STR="Hello World"
bash: STR-STR=Hello World: command not found

answered Oct 20, 2023 at 0:42

Zhenya

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