Regular expressions n n n Used by several

Regular expressions n n n 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 n n n (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

Regular expressions n n n n (continue. ) ^$ matches any line that contains no characters […] is used to match any character enclosed in […] [t. T] 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

Regular expressions n n n (continue. ) (*) 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] * matches any alphabetic character followed by zero or more alphabetic character

Regular expressions n n (continue. ) [-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)

Regular expressions n n (continue. ) {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-z. A-Z]{7} matches exactly seven alphabetic characters

Regular expressions n n n (continue. ) 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

Regular expressions n n (continue. ) ^(. ). *1$ matches all lines in which the first character on the line is the same as the last. Note (. *) matches all the characters inbetween ^(…)(…) the first three characters on the line will be stored into register 1 and the next three characters into register 2

cut n Used in extracting various fields of data from a data file or the output of a command $ who bgeorge abakshi tphilip pts/16 pts/13 pts/11 Oct Oct 5 15: 01 6 19: 48 2 14: 10 (216. 87. 102. 204) (216. 87. 102. 220) (AC 8 C 6085. ipt. aol. com) $ who | cut -c 1 -8, 18 bgeorge abakshi tphilip Oct Oct 5 15: 01 6 19: 48 2 14: 10 (216. 87. 102. 204) (216. 87. 102. 220) (AC 8 C 6085. ipt. aol. com) $ Format: cut -cchars file n chars specifies what characters to extract from each line of file.

cut (continue. ) n n n Example: -c 5, -c 1, 3, 4 -c-10 -15 -c 5 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: Nobody: /: noaccess: x: 60002: No Access User: /: oracle: *: 101: 67: DBA Account: /export/home/oracle: /bin/csh webuser: *: 102: Web User: /export/home/webuser: /bin/csh abuzneid: x: 103: 100: Abdelshakour Abuzneid: /home/abuzneid: /sbin/csh $

cut (continue. ) $ cut -d: -f 1 /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 -f 1 phonebook Edward Alice Sony Robert $

paste n n Format: paste files tab character is a default delimiter

paste (continue. ) n 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. ) n n The option –s tells paste together lines from the same file not from alternate files To change the delimiter, -d option is used

paste (continue. ) n 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 n n n n 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: 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. ) n n n 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, 2 p’ file which prints the first two lines Example: sed –n ‘/UNIX/p’ file, prints any line containing UNIX

sed (continue. ) n n Example: sed –n ‘/1, 2 d/’ 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 n n n 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 Bell Backspace Tab New line Linefeed Form feed Carriage return Escape Octal value 7 10 11 12 12 14 15 33

tr (continue. ) n n 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. ) n n 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 n n 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. ) n Example : grep * smarts will give an error because * will be substituted with all file in the correct directory n Example : grep ‘*’ smarts grep arguments * smarts

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

sort (continue. ) $ echo Ash >> students $ cat students Sue Vara Elvis Luis Eliza Ash $ sort students Ash Eliza Elvis Luis Sue Vara $

sort (continue. ) n n n 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 +1 n data -9 -3 3 1 15 2 -10 11 2 13 20 22 $

sort (continue. ) n n To sort by the second field +1 n should be used instead of n. +1 says to skip the first field +5 n would mean to skip the first five fields on each line and then sort the data numerically

sort n (continue. ) Example $ sort -t: +2 n /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: Web User: /export/home/webuser: /bin/csh y: x: 60001: Nobody: /: $

uniq n n 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. ) n The –d option is used to list duplicate lines n Example: $ cat students Sue Vara Elvis Luis Eliza Ash $ uniq students Sue Vara Elvis Luis Eliza Ash $

References n n n 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