Shell Programming and Scripting

You are providing the regular expression as a string literal. Strings literals have to be parsed. The string parser has its own set of escape sequences. The \\ sequences that you intend for the regular expression are being interpreted by the string parser first, and for each such pair it emits a single backslash. You can confirm this by printing the variable's value.

At a later time, the string-valued variable is used where a regular expression is expected. AWK then passes this string to the regular expression parser for compilation. At this point, the error occurs.

You have two choices. You can double the number of backslases or you can specify the regular expression using a regular expression literal instead of a string literal (/pattern/ instead of "pattern").

For more info, see Computed Regexps - The GNU Awk User's Guide (this applies to all awk implementations, not just gawk).

Regards,
Alister

---------- Post updated at 11:58 AM ---------- Previous update was at 11:53 AM ----------

Since they occur within single quotes, the shell isn't consuming any backslashes. As I said above, it's awk's string parser.

An improved version of your suggestion:

Code:

awk '$0 ~ /pattern_with_half_the_backslashes/' netgroup

Regards,
Alister

Thanks guys I know something was consuming the additional backslashes.