Linked Questions
24 questions linked to/from Why can't I specify an environment variable and echo it in the same command line?
11
votes
2
answers
3k
views
Bash: assignment of variable on same line not altering echo behavior [duplicate]
a=2
a=3 echo $a #prints 2
can someone explain why would anyone use the above code in line-2.
a=3 will be ignored as there is no "enter" after it.
But I saw it in script like above and not sure ...
- 121
5
votes
2
answers
12k
views
Variable value doesn't change in bash script [duplicate]
Running the following code:
a=one; echo $a
a=two echo $a
a=three echo $a >$a
results in
one
one
and a created file with name "one" with content "one"
Why the variable didn't change to two at ...
- 317
6
votes
2
answers
10k
views
How to start a command in bash with multiple environment variables set [duplicate]
With one environment variable it goes like:
bash$> foo=1 echo "$foo"
1
[EDIT: as noted below, even that won't work but worked only because $foo was previously set by some other trial. Should had ...
- 171
1
vote
1
answer
3k
views
Bash: inject variable in command, that sets an env variable [duplicate]
With bash, I'm trying to set environment variables for a given command by injecting another variable before running said command:
It's easier to describe that with an example:
setHELLO="HELLO=42&...
- 4,536
2
votes
2
answers
760
views
In Bash, why `x=100 echo $x` doesn't print anything? [duplicate]
I saw codes like this:
fqdn='computer1.daveeddy.com'
IFS=. read hostname domain tld <<< "$fqdn"
echo "$hostname is in $domain.$tld"
# => "computer1 is in daveeddy.com"
I think it works ...
- 47.3k
5
votes
2
answers
278
views
Why does "A=3; A=4 echo $A" produce 3 (instead of 4) in Bash? [duplicate]
If I understand correctly, the syntax
Var=<something> command
should run the command after setting Var to "something". Then why does "A=3; A=4 echo $A" produces 3 in my bash?
- 10.3k
0
votes
2
answers
1k
views
assign and expand shell variable in same command line [duplicate]
I want to assign one or multiple variables at the beginning of a command line in my shell to reuse it in the command invocation. I'm confused of how my shell behaves and want to understand what is ...
- 2,941
0
votes
2
answers
1k
views
Inline BASH variable, can't get the command to receive it [duplicate]
Why doesn't this work?
HELLO=WORLD echo $HELLO
In my shell it outputs
- 776
7
votes
0
answers
800
views
Assign and use of a variable in the same subshell [duplicate]
I was doing something very simple like: v=5 echo "$v" and expected it to print 5. However, it does not. The value that was just set is not available for the next command.
I recently learnt that "In ...
- 293k
3
votes
1
answer
308
views
Why doesn't ''var=value echo $var'' emit value? [duplicate]
Wanted to validate my understanding of why these situations behave differently:
I think #1 happens because the assignment and echo run as a single command in the shell and $SOME_VAR is not set when ...
- 24.9k
0
votes
1
answer
285
views
Why do bash environment variables differ in shell versus node? [duplicate]
Run these commands in Bash:
NODE_ENV=production echo $NODE_ENV outputs ""
NODE_ENV=production && echo $NODE_ENV outputs "production"
export NODE_ENV=production && echo $NODE_ENV ...
- 475
2
votes
1
answer
486
views
Bash: 'echo' not outputting variable defined on same line [duplicate]
This echo call outputs the variable:
$ FOO="bar" eval 'echo foo: "$FOO"'
foo: bar
But this one does not:
$ FOO="bar" echo foo: "$FOO"
foo:
Why is that? I'm pretty sure I have the single and double ...
- 442
0
votes
1
answer
280
views
How to dynamically compute value of a variable and use it in a command? [duplicate]
Reducing what I'm trying to do to a simple example:
env temp=`pwd` echo "$temp"
I get this message:
temp: Undefined variable.
How do I make it work (in a shell-agnostic way)? I'm expecting the ...
- 3
2
votes
1
answer
72
views
Why environment variables aren't being passed in a single command [duplicate]
In bash, I can pass an environment variable to a single command in the following way:
KEY=VAL <command>
However, I don't understand why the following doesn't work:
KEY=VAL echo $KEY
While this ...
- 4,113
0
votes
1
answer
75
views
How python can execute shell command with env [duplicate]
Basically, os.system() can execute shall commands, such as:
os.system("echo $A")
It will work well and output value environment variable A.
But this seems to not work:
os.system("A=b ...
- 10.1k