How to retrieve the variable name “apple” in "FRUIT=apple" in UNIX shell?

Question

When the user inputs FRUIT=apple in the Unix shell, how can I get the name FRUIT and apple from the input FRUIT=apple separately?

echo -e "\nEnter inputs here: \c"
read inputs

## user input "FRUIT=apple"

Is there any way to get a partial text from the input? Can we use the expr command to solve the problem? If so, how?

You shouldn't add the solution you used to the question. The question should only contain the, well, question. — Benjamin W., Sep 29 '19 at 19:20
You also changed the question to remove any mention of `expr`, which makes for example my answer look strange - why would I mention `expr` in there. I suggest you roll back your edit. — Benjamin W., Sep 29 '19 at 19:21

score 2 · Answer 1 · answered Sep 27 '19 at 08:34

2

You can do it this way, for example:

$ IFS== read -r key value
FRUIT=apple
$ echo "$key"
FRUIT
$ echo "$value"
apple

answered Sep 27 '19 at 08:34

l0b0

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score 2 · Answer 2 · edited Sep 27 '19 at 13:26

2

Try using cut command and pass the delimiter as "=" . The right side of the same will be apple and left side will be FRUIT.

cat file_name | cut -d "=" -f1

edited Sep 27 '19 at 13:26

Benjamin W.

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answered Sep 27 '19 at 12:29

Sarthak Nayak

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Benjamin W. · Answer 3 · 2019-09-27T13:59:20.210

You could use expr with regular expressions like this:

$ str='FRUIT=apple'
$ key=$(expr "$str" : '\([^=]*\)')
$ value=$(expr "$str" : '.*=\([^=]*\)')
$ echo "<$key> <$value>"
<FRUIT> <apple>

The expression expr string : regex returns the number of characters matched, or (as used above) if there is a capture group $...$, it'll return that capture group. The regex starts with an implicit ^ anchor.

The expression for key matches everything up to the first = sign; the one for value captures everything after the (last) = sign.

All this being said, expr is a holdover from when shells weren't powerful enough to do text processing using built-ins; any modern shell can do it. For example:

Splitting on = and reading into two variables:
```
IFS='=' read -r key value <<< "$str"
```
Using parameter expansion:
```
key=${str%=*}
value=${str#*=}
```

Thank you for the answer, the sum-up and explanation are clear. I was using `key=${str%=*} value=${str#*=}` as the solution. — John Xiating Cai, Sep 29 '19 at 14:07

How to retrieve the variable name “apple” in "FRUIT=apple" in UNIX shell?

3 Answers3