CODEWITHSUNDEEP
bash
XINDI LI
XINDI LI

Reputation: 675

How to replace bash variable with command line arguments

My bash script bash.sh only contains one line

echo "${abc:=123}"

I learned that := is used to assign default values. So when I run bash.sh abc=abc, I expect the output to be abc.

However, the output is still 123.

Why is that? Am I call the script in the wrong way? Thanks.

Upvotes: 0

Views: 1220

Answers (2)

that other guy
that other guy

Reputation: 123410

You are passing a parameter and expecting to see it in an environment variable.

If you want to set an environment variable, you can do that before the script name:

$ cat foo
#!/bin/bash
echo "${abc:=123}"

$ ./foo
123

$ abc=hello ./foo
hello

Upvotes: 1

R. Arctor
R. Arctor

Reputation: 728

Bash positional arguments are set to $1, $2, etc. Change your script to:

abc=$1
echo "${abc:=123}"

this will make it so if the variable abc is unset the default value is echoed but if another value is passed on the command line abc will be set to that value.

Upvotes: 1

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