CODEWITHSUNDEEP
bashenvironment-variables
S.G
S.G

Reputation: 163

Exporting variables with eval not working as expected

I've got a file with variable exports like this:

$ cat file.txt
export A=foo
export B=\"B-\$A\" # I want export another var, which depends on a previously exported var

Using eval to execute those statements does not produce the expected behavior:

$ eval $(cat file.txt)
$ echo ${B:-unset}
unset

When not using export, it works as expected:

$ eval $(echo "A=foo B=\"B-\$A\"")
$ echo ${B:-unset}
B-foo

Why the difference, and is there any way to achieve the same result without removing the export from the variable A (that part of the file comes from an external source outside my control, but I can change the variable B)?

Upvotes: 1

Views: 2865

Answers (1)

John Zwinck
John Zwinck

Reputation: 249642

First, change file.txt to this (and consider naming it file.sh instead):

export A=foo
export B="B-$A"

Then, instead of eval $(cat file.txt), do this:

source file.txt

That does the same thing as if you had pasted the content file.txt into your shell.

Upvotes: 2

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