How to avoid using escape characters in grep?
The \\ (single backslash) character tells the grep command to treat the following character (in this example the $) as a literal character rather than an expression character. Use the fgrep command to avoid the necessity of using escape characters such as the backslash.
How to escape a dollar sign in grep?
The (single backslash) character tells the grep command to treat the following character (in this example the $) as a literal character rather than an expression character. Use the fgrep command to avoid the necessity of using escape characters such as the backslash.
Is the character in grep always special in Ere?
¹ Note also that if you ever switch to Extended Regular Expressions (ERE), e.g. if you decided to use egrep (or grep -E ), the $ character is always special. In ERE’s $Id$ would never match anything because you can’t have characters after the end of a line, so \\$Id\\$ would be the only way to go.
When to use grep at the end of a line?
As explained in (1.), this regex matches a literal $Id only at the end of a line because the first $ is literal while the second is a special anchor character. ¹ Note also that if you ever switch to Extended Regular Expressions (ERE), e.g. if you decided to use egrep (or grep -E ), the $ character is always special.
Is the$ at the end of an expression in grep?
grep uses Basic Regular Expressions (BRE), and $ is a special character in BRE’s only at the end of an expression. The consequence of this is that the 2 instances of $ in $Id$ are not equal. The first one is a normal character and the second is an anchor that matches the end of the line.
Why does grep fail to escape the pipe in regex?
The first fails because grep escapes the pipe programmatically, resulting in a literal pipe in the regex. The last attempts fails because \\\\\\| results in a literal backslash then a literal pipe in the regex. According to grep man pages, and especially according to info pages, all examples given for grep include single quotes and not double quotes.