Regular expressions Used by several different UNIX commands, including ed, sed, awk, grep A period ‘.’ matches any single characters.X. matches any X.

Regular expressions

Used by several different UNIX commands, including ed, sed, awk, grep

A period ‘.’ matches any single characters .X. matches any X that is surrounded by any two

characters Caret character ^ matches the beginning of the

line ^Bridgeport matches the characters Bridgeport

only if they occur at the beginning of the line

Regular expressions (continue.)

A dollar sign ‘$’ is used to match the end of the line

Bridgeport$ will match the characters Bridgeport only they are the very last characters on the line

$ matches any single character at the end of the line

To match any single character, this character should be preceded by a backslash ‘\’ to remove the special meaning

\.$ matches any line end with a period


^$ matches any line that contains no characters […] is used to match any character enclosed in

[…] [tT] matches a lower or upper case t followed

immediately by the characters [A-Z] matches upper case letter [A-Za-z] matches upper or lower case letter [^A-Z] matches any character except upper case

letter [A-Za-z] matches any non alphabetic character


(*) Asterisk matches zero or more characters X* matches zero, one, two, three, … capital X’s XX* matches one or more capital X’s .* matches zero or more occurrences of any

characters e.*e matches all the characters from the first e in the

line to the last one [A-Za-z] [A-Za-z] * matches any alphabetic

character followed by zero or more alphabetic character


[-0-9] matches a single dash or digit character (ORDER IS IMPORTANT)

[0-9-] same as [-0-9] [^-0-9] matches any alphabetic except digits and

dash []a-z] matches a right bracket or lower case letter

(ORDER IS IMPORTANT)


\{min, max\} matches a precise number of characters

min specifies the minimum number of occurrences of the preceding regular expression to be matched, and max specifies the maximum

w\{1,10\} matches from 1 to 10 consecutive w’s [a-zA-Z]\{7\} matches exactly seven alphabetic

characters


X\{5,\} matches at least five consecutive X’s $….) is used to save matched characters ^\(.$ matches the first character on the line and

store it into register one There is 1-9 registers To retrieve what is stored in any register \n is used Example: ^$.$\1 matches the first two characters

on a line if they are both the same characters


^$.$.*\1$ matches all lines in which the first character on the line is the same as the last. Note (.*) matches all the characters in-between

^$…)\(…$ the first three characters on the line will be stored into register 1 and the next three characters into register 2

cut

$ whobgeorge pts/16 Oct 5 15:01 (216.87.102.204)

abakshi pts/13 Oct 6 19:48 (216.87.102.220)

tphilip pts/11 Oct 2 14:10 (AC8C6085.ipt.aol.com)

$ who | cut -c1-8,18-bgeorge Oct 5 15:01 (216.87.102.204)

abakshi Oct 6 19:48 (216.87.102.220)

tphilip Oct 2 14:10 (AC8C6085.ipt.aol.com)

$

Used in extracting various fields of data from a data

file or the output of a command

Format: cut -cchars file

chars specifies what characters to extract from each line of file.

cut (continue.)

Example: -c5, -c1,3,4 -c-10-15 -c5- The –d and –f options are used with cut

when you have data that is delimited by a particular character

Format: cut –ddchars –ffields file dchar: delimiters of the fields (default: tab

character) fields: fields to be extracted from file

cut (continue.)

$ cat /etc/passwd

root:x:0:1:Super-User:/:/sbin/sh

daemon:x:1:1::/:

bin:x:2:2::/usr/bin:

sys:x:3:3::/:

adm:x:4:4:Admin:/var/adm:

lp:x:71:8:Line Printer Admin:/usr/spool/lp:

uucp:x:5:5:uucp Admin:/usr/lib/uucp:

listen:x:37:4:Network Admin:/usr/net/nls:

nobody:x:60001:60001:Nobody:/:

noaccess:x:60002:60002:No Access User:/:

oracle:*:101:67:DBA Account:/export/home/oracle:/bin/csh

webuser:*:102:102:Web User:/export/home/webuser:/bin/csh

abuzneid:x:103:100:Abdelshakour Abuzneid:/home/abuzneid:/sbin/csh

$

cut (continue.)

$ cut -d: -f1 /etc/passwd

root

daemon

bin

sys

adm

lp

uucp

nuucp

listen

nobody

oracle

webuser

abuzneid

$

cut (continue.)

$ cat phonebook

Edward 336-145

Alice 334-121

Sony 332-336

Robert 326-056

$ cut -f1 phonebook

Edward

Alice

Sony

Robert

$

paste

Format: paste files tab character is a default delimiter

paste (continue.)

Example:

$ cat students

Sue

Vara

Elvis

Luis

Eliza

$ cat sid

578426

452869

354896

455468

335123

$ paste students sid

Sue 578426

Vara 452869

Elvis 354896

Luis 455468

Eliza 335123

$

paste (continue.)

The option –s tells paste to paste together lines from the same file not from alternate files

To change the delimiter, -d option is used

paste (continue.)

Examples:$ paste -d '+' students sid

Sue+578426

Vara+452869

Elvis+354896

Luis+455468

Eliza+335123

$ paste -s students

Sue Vara Elvis Luis Eliza

$ ls | paste -d ' ' -s -

addr args list mail memo name nsmail phonebook programs roster sid

students test tp twice user

$

sed

sed (stream editor) is a program used for editing data

Unlike ed, sed can not be used interactively Format: sed command file command: applied to each line of the specified file file: if no file is specified, then standard input is

assumed sed writes the output to the standard output s/Unix/UNIX command is applied to every line in

the file, it replaces the first Unix with UNIX

sed (continue.)

sed makes no changes to the original input file ‘s/Unix/UNIX/g’ command is applied to every line

in the file. It replaces every Unix with UNIX. “g” means global

With –n option, selected lines can be printed Example: sed –n ’1,2p’ file which prints the first

two lines Example: sed –n ‘/UNIX/p’ file, prints any line

containing UNIX

sed (continue.)

Example: sed –n ‘/1,2d/’ file, deletes lines 1 and 2

Example: sed –n’ /1’ text, prints all lines from text, showing non printing characters as \nn and tab characters as “>”

tr

The tr filter is used to translate characters from standard input

Format: tr from-chars to-chars Result is written to standard output Example tr e x <file, translates every “e” in file to

“x” and prints the output to the standard output The octal representation of a character can be

given to “tr” in the format \nnn Example: tr : ‘\11’ will translate all : to tabs

tr (continue.)

Character Octal value

Bell 7

Backspace 10

Tab 11

New line 12

Linefeed 12

Form feed 14

Carriage return 15

Escape 33

tr (continue.)

Example: tr ‘[a-z]’’[A-Z]’ < file translate all lower case letters in file to their uppercase equivalent. The characters ranges [a-z] and [A-Z] are enclosed in quotes to keep the shell from replacing them with all files named from a through z and A through Z

To “squeeze” out multiple occurrences of characters the –s option is used

tr (continue.)

Example: tr –s ’ ’ ‘ ‘ < file will squeeze multiple spaces to one space

The –d option is used to delete single characters from a stream of input

Format: tr –d from-chars Example: tr –d ‘ ‘ < file will delete all spaces from

the input stream

grep

Searches one or more files for a particular characters patterns

Format: grep pattern files Example: grep path .cshrc will print every line

in .cshrc file which has the pattern ‘path’ and print it

Example: grep bin .cshrc .login .profile will print every line from any of the three files .cshrc, .login and .profile which has the pattern “bin”

grep (continue.)

Example : grep * smarts will give an error because * will be substituted with all file in the correct directory

Example : grep ‘*’ smarts

*

smartsgrep

arguments

sort

By default, sort takes each line of the specified input file and sorts it into ascending order$ cat students

Sue

Vara

Elvis

Luis

Eliza

$ sort students

Eliza

Elvis

Luis

Sue

Vara

$

sort (continue.)

The –n option tells sort to eliminate duplicate lines from the output

sort (continue.)

$ echo Ash >> students

$ echo Ash >> students

$ cat students

Sue

Vara

Elvis

Luis

Eliza

Ash

Ash

$ sort students

Ash

Ash

Eliza

Elvis

Luis

Sue

Vara

$

sort (continue.)

The –s option reverses the order of the sort The –o option is used to direct the input from the

standard output to file sort students > sorted_students works as sort

students –o sorted_students The –o option allows to sort file and saves the output

to the same file Example:

sort students –o students correct

sort students > students incorrect

sort (continue.)

• The –n option specifies the first field for sort as number and data to sorted arithmetically

sort (continue.)

$ cat data

-10 11

15 2

-9 -3

2 13

20 22

3 1

$ sort data

-10 11

-9 -3

15 2

2 13

20 22

3 1

$

sort (continue.)

$ sort -n data

-10 11

-9 -3

2 13

3 1

15 2

20 22

$ sort +1n data

-9 -3

3 1

15 2

-10 11

2 13

20 22

$

sort (continue.)

To sort by the second field +1n should be used instead of n. +1 says to skip the first field

+5n would mean to skip the first five fields on each line and then sort the data numerically

sort (continue.)

Example

$ sort -t: +2n /etc/passwd

root:x:0:1:Super-User:/:/sbin/sh

daemon:x:1:1::/:

bin:x:2:2::/usr/bin:

sys:x:3:3::/:

adm:x:4:4:Admin:/var/adm:

uucp:x:5:5:uucp Admin:/usr/lib/uucp:

nuucp:x:9:9:uucp Admin:/var/spool/uucppublic:/usr/lib/uucp/uucico

listen:x:37:4:Network Admin:/usr/net/nls:

lp:x:71:8:Line Printer Admin:/usr/spool/lp:

oracle:*:101:67:DBA Account:/export/home/oracle:/bin/csh

webuser:*:102:102:Web User:/export/home/webuser:/bin/csh

y:x:60001:60001:Nobody:/:

$

uniq

Used to find duplicate lines in a file Format: uniq in_file out_file uniq will copy in_file to out_file removing

any duplicate lines in the process uniq’s definition of duplicated lines are

consecutive-occurring lines that match exactly

uniq (continue.)

$ cat studentsSueVaraElvisLuisElizaAshAsh

$ uniq studentsSueVaraElvisLuisElizaAsh

$

The –d option is used to list duplicate lines

Example:

References UNIX SHELLS BY EXAMPLE BY ELLIE

QUIGLEY UNIX FOR PROGRAMMERS AND

USERS BY G. GLASS AND K ABLES UNIX SHELL PROGRAMMING BY S.

KOCHAN AND P. WOOD

Regular expressions Used by several different UNIX commands, including ed, sed, awk, grep A period ‘.’ matches any single characters.X. matches any X.

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