IFS Internal Field Separator in Bash Scripting

IFS stands for  Internal Field Separator - it's a character that separate fields. In the example you posted it is set to new line character (\n), so after setting it for will process text line by line. In that example you could change value of $IFS (to some letter that you have in your input file) and check how text will be splitted.

 

[root@ip-192-168-1-36 tmp]# for i in `cat sample.txt`; do echo $i; done
Mar 10
Mar 11
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[root@ip-192-168-1-36 tmp]# IFS=$' '
[root@ip-192-168-1-36 tmp]# for i in `cat sample.txt`; do echo $i; done

Mar
10
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11
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7
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[root@ip-192-168-1-36 tmp]# IFS=$'\n'
[root@ip-192-168-1-36 tmp]# for i in `cat sample.txt`; do echo $i; done
Mar 10
Mar 11
Mar 7
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[root@ip-192-168-1-36 tmp]#