Question

I am having trouble understanding the -c option in tr (Unix command).

Looking at this format for tr: tr [Options] set1 [set2]

I understand that -c is an [option] available for tr which means that “it takes the complement of set1 ( aka, all characters not in set1). But, can someone please give an example of how to use this command and explain the benefits.

Thank you

Answer 1

It means to complement the character range. When you complement the string A-Z you get Any character that is not in A … Z.

Sometimes it is much easier to specify a task with the complement. Suppose you want to count the number of semicolons in a C source file. You delete all non-semicolons and count what’s left:

tr -d -c \; < file.c | wc -c