[Linux 常見問題] Bash - How to process each output line in a loop?

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Question
I have a number of lines retrieved from a file after running the grep command as follows:

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1. var=`grep xyz abc.txt`  

Let’s say I got 10 lines which consists of xyz as a result.

Now I need to process each line I got as a result of the grep command. How do I proceed with this?

HowTo
One of the easy ways is not to store the output in a variable, but directly iterate over it with a while/read loop. Something like:
- test.sh

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1. #!/bin/sh  
2. grep xyz abc.txt | while read -r line ; do  
3.     echo "Processing $line"  
4.     # your code goes here  
5. done  

There are variations on this scheme depending on exactly what you're after. A sample usage:

root@localhost:demo_bash# cat abc.txt
xyz 123
test line1
456 xyz
test line2

root@localhost:demo_bash# ./test.sh
Processing xyz 123
Processing 456 xyz