Editing Regular expression (section)

===Delimiters===
When entering a regex in a programming language, they may be represented as a usual string literal, hence usually quoted; this is common in C, Java, and Python for instance, where the regex <code>re</code> is entered as <code>"re"</code>. However, they are often written with slashes as [[delimiter]]s, as in <code>/re/</code> for the regex <code>re</code>. This originates in [[ed (text editor)|ed]], where <code>/</code> is the editor command for searching, and an expression <code>/re/</code> can be used to specify a range of lines (matching the pattern), which can be combined with other commands on either side, most famously <code>g/re/p</code> as in [[grep]] ("global regex print"), which is included in most [[Unix]]-based operating systems, such as [[Linux]] distributions. A similar convention is used in [[sed]], where search and replace is given by <code>s/re/replacement/</code> and patterns can be joined with a comma to specify a range of lines as in <code>/re1/,/re2/</code>. This notation is particularly well known due to its use in [[Perl]], where it forms part of the syntax distinct from normal string literals. In some cases, such as sed and Perl, alternative delimiters can be used to avoid collision with contents, and to avoid having to escape occurrences of the delimiter character in the contents. For example, in sed the command <code>s,/,X,</code> will replace a <code>/</code> with an <code>X</code>, using commas as delimiters.