4.5. egrep (Extended grep ) The main advantage of using egrep is that additional regular expression metacharacters (see Table 4.4) have been added to the set provided by grep . The \(\) and \{ \} , however, are not allowed. (See GNU grep “E if using Linux.) Table 4.4. egrep 's Regular Expression Metacharacters | Metacharacter | Function | Example | What It Matches | | ^ | Beginning-of-line anchor | '^love' | Matches all lines beginning with love . | | $ | End-of-line anchor | 'love$' | Matches all lines ending with love . | | . | Matches one character | 'l..e' | Matches lines containing an l , followed by two characters , followed by an e . | | * | Matches zero or more of the characters preceding the asterisk | ' *love' | Matches lines with zero or more spaces followed by the pattern love . | | [ ] | Matches one character in the set | '[Ll]ove' | Matches lines containing love or Love . | | [^ ] | Matches one character not in the set | '[^A “KM “Z]ove' | Matches lines not containing A through K or M through Z , followed by ove . | | New with egrep | | + | Matches one or more of the characters preceding the + sign | '[a “z]+ove' | Matches one or more lowercase letters , followed by ove . Would find move , approve , love , behoove , etc. | | ? | Matches zero or one of the preceding characters | 'lo?ve' | Matches for an l followed by either one or not any occurrences of the letter o . Would find love or lve . | | ab | Matches either a or b | 'lovehate' | Matches for either expression, love or hate . | | () | Groups characters | 'love(ablely)' '(ov)+' | Matches for lovable or lovely . Matches for one or more occurrences of ov . |
4.5.1 egrep Examples The following examples illustrate only the way the new extended set of regular expression metacharacters is used with egrep . The grep examples presented earlier illustrate the use of the standard metacharacters, which behave the same way with egrep . Egrep also uses the same options at the command line as grep . The following datafile is used in the examples in this section. | % cat datafile | | northwest | NW | Charles Main | 3.0 | .98 | 3 | 34 | | western | WE | Sharon Gray | 5.3 | .97 | 5 | 23 | | southwest | SW | Lewis Dalsass | 2.7 | .8 | 2 | 18 | | southern | SO | Suan Chin | 5.1 | .95 | 4 | 15 | | southeast | SE | Patricia Hemenway | 4.0 | .7 | 4 | 17 | | eastern | EA | TB Savage | 4.4 | .84 | 5 | 20 | | northeast | NE | AM Main Jr. | 5.1 | .94 | 3 | 13 | | north | NO | Margot Weber | 4.5 | .89 | 5 | 9 | | central | CT | Ann Stephens | 5.7 | .94 | 5 | 13 |
Example 4.30. % egrep 'NWEA' datafile northwest NW Charles Main 3.0 .98 3 34 eastern EA TB Savage 4.4 .84 5 20
EXPLANATION Prints the line if it contains either the expression NW or the expression EA . Example 4.31. % egrep '3+' datafile northwest NW Charles Main 3.0 .98 3 34 western WE Sharon Gray 5.3 .97 5 23 northeast NE AM Main Jr. 5.1 .94 3 13 central CT Ann Stephens 5.7 .94 5 13
EXPLANATION Prints all lines containing one or more occurrences of the number 3 ; e.g., 3 , 33 , 33333333 . Example 4.32. % egrep '2\.?[09]' datafile western WE Sharon Gray 5.3 .97 5 23 southwest SW Lewis Dalsass 2.7 .8 2 18 eastern EA TB Savage 4.4 .84 5 20
EXPLANATION Prints all lines containing a 2 , followed by one period or no period at all, followed by a number; e.g., matches 2.5 , 25 , 29 , 2.3 , etc. Example 4.33. % egrep '(no)+' datafile northwest NW Charles Main 3.0 .98 3 34 northeast NE AM Main Jr. 5.1 .94 3 13 north NO Margot Weber 4.5 .89 5 9
EXPLANATION Prints lines containing one or more consecutive occurrences of the pattern group no ; e.g., no , nono , nononononono , etc. Example 4.34. % egrep 'S(hu)' datafile western WE Sharon Gray 5.3 .97 5 23 southern SO Suan Chin 5.1 .95 4 15
EXPLANATION Prints all lines containing S , followed by either h or u ; e.g., Sh aron or Su an . Example 4.35. % egrep 'Shu' datafile western WE Sharon Gray 5.3 .97 5 23 southern SO Suan Chin 5.1 .95 4 15 southwest SW Lewis Dalsass 2.7 .8 2 18 southeast SE Patricia Hemenway 4.0 .7 4 17
EXPLANATION Prints all lines containing the expression Sh or u ; e.g., Sh aron or so u thern . 4.5.2 egrep Review Table 4.5 contains examples of egrep commands and what they do. Table 4.5. Review of egrep | Command | What It Does | | egrep '^ +' file | Prints lines beginning with one or more spaces. | | egrep '^ *' file | Prints lines beginning with zero or more spaces. [a] | | egrep '(TomDan) Savage' file | Prints lines containing Tom Savage or Dan Savage . | | egrep '(ab)+' file | Prints lines with one or more occurrences of ab . | | egrep '^X[0 “9]?' file | Prints lines beginning with X followed by zero or one single digit. | | egrep 'fun\.$' * | Prints lines ending in fun . from all files. [a] | | egrep '[A “Z]+' file | Prints lines containing one or more capital letters. | | egrep '[0 “9]' file | Prints lines containing a number. [a] | | egrep '[A “Z]...[0 “9]' file | Prints lines containing five-character patterns starting with a capital letter, followed by three of any character, and ending with a number. [a] | | egrep '[tT]est' files | Prints lines with Test and/or test . [a] | | egrep '(SusanJean) Doe' file | Prints lines containing Susan Doe or Jean Doe . | | egrep “v 'Mary' file | Prints all lines not containing Mary . [a] | | egrep “i 'sam' file | Prints all lines containing sam , regardless of case (e.g., SAM , sam , SaM , sAm ). [a] | | egrep “l 'Dear Boss' * | Lists all filenames containing Dear Boss . [a] | | egrep “n 'Tom' file | Precedes matching lines with line numbers . [a] | | egrep “s "$ name " file | Expands variable name, finds it, but prints nothing. Can be used to check the exit status of egrep . [a] (s stands for silent) |
[a] egrep and grep handle this pattern in the same way. |
