If you don't have any lines that contain both MOD and DEL in your file, then grep MOD | grep DEL not printing anything seems quite correct to me.

Let me ask it this way, given the file with no lines containing MOD and DEL, which lines do you want to have printed?

In reply to Re^5: what is grep command for and condition by JavaFan
in thread OT: what is grep command for and condition by anakin30

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