Changes

Tutorial9: Regular Expressions

7 bytes added, 09:16, 13 March 2021

→‎INVESTIGATION 1: SIMPLE & COMPLEX REGULAR EXPRESSIONS

# Issue the following Linux command to match strings that '''begin and end with 3 characters''': grep "^...$" textfile1.txt What do you notice compared to the previous command?

# Issue the following Linux command to match strings that '''begin with 3 digits''': grep "^[0-9][0-9][0-9]" textfile1.txt What did you notice?

# Issue the following Linux command to match strings that '''end with 3 uppercase letters''': grep "[A-Z][A-Z][A-Z]$" textfile1.txt <table align="right"><tr valign="top"><td>[[Image:regexps-6.png|thumb|right|220px|Anchoring '''3 digits''' at the '''beginning''' and '''ending''' of text.]]</td><td>[[Image:regexps-7.png|thumb|right|250px|Anchoring '''3 alpha-numeric characters''' at the '''beginning''' and '''ending''' of text.]]</td></tr></table>~~Did any lines~~ What type of strings match this pattern?

# Issue the following Linux command to match strings that consist of only 3 digits: grep "^[0-9][0-9][0-9]$" textfile1.txt What did you notice?

# Issue the following Linux command to match strings that consist of only 3 alphanumeric digits: grep "^[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]$" textfile1.txt What did you notice? The "*" complex regular expression symbol is often confused with the "*" '''filename expansion''' symbol. In other words, it does NOT represent zero or more of '''any character''', but zero or more '''occurrences''' of the character that comes '''before''' the "*" symbol.

Msaul

Administrators

13,420

edits

CDOT Wiki β

Changes

Tutorial9: Regular Expressions

CDOT Wiki ^β