Prsentation PowerPoint

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Important UNIX Utilities
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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

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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

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Regular expressions (continue.)

• 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

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Regular expressions (continue.)

• () Asterisk matches zero or more characters
• X matches zero, one, two, three, capital Xs
• XX matches one or more capital Xs
• . 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

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Regular expressions (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)

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Regular expressions (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 ws
• a-zA-Z\7\ matches exactly seven alphabetic
  characters

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Regular expressions (continue.)

• X\5,\ matches at least five consecutive Xs
• \(.) 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

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Regular expressions (continue.)

• \(.\).\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

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cut

• Used in extracting various fields of data from a
  data
• file or the output of a command

• who
• bgeorge pts/16 Oct 5 1501
  (216.87.102.204)
• abakshi pts/13 Oct 6 1948
  (216.87.102.220)
• tphilip pts/11 Oct 2 1410
  (AC8C6085.ipt.aol.com)
• who cut -c1-8,18-
• bgeorge Oct 5 1501 (216.87.102.204)
• abakshi Oct 6 1948 (216.87.102.220)
• tphilip Oct 2 1410
  (AC8C6085.ipt.aol.com)

• Format cut -cchars file
• chars specifies what characters to extract from
  each line of file.

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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

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cut (continue.)
cat /etc/passwd rootx01Super-User//sbin/sh
daemonx11/ binx22/usr/bin sysx33
/ admx44Admin/var/adm lpx718Line
Printer Admin/usr/spool/lp uucpx55uucp
Admin/usr/lib/uucp listenx374Network
Admin/usr/net/nls nobodyx6000160001Nobody/
noaccessx6000260002No Access
User/ oracle10167DBA Account/export/home/o
racle/bin/csh webuser102102Web
User/export/home/webuser/bin/csh abuzneidx103
100Abdelshakour Abuzneid/home/abuzneid/sbin/csh

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cut (continue.)
cut -d -f1 /etc/passwd root daemon bin sys adm
lp uucp nuucp listen nobody oracle webuser abuznei
d
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cut (continue.)
cat phonebook Edward 336-145 Alice
334-121 Sony 332-336 Robert 326-056 cut
-f1 phonebook Edward Alice Sony Robert
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paste

• Format paste files
• tab character is a default delimiter

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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
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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

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paste (continue.)

• Examples

paste -d '' students sid Sue578426 Vara452869
Elvis354896 Luis455468 Eliza335123 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
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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

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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

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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

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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 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

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tr (continue.)
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tr (continue.)

• Example tr a-zA-Z 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

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tr (continue.)

• Example tr s 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 from the input stream

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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

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grep (continue.)

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

smarts
grep
arguments
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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
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sort (continue.)

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

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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
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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

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sort (continue.)

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

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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
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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
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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

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sort (continue.)

• Example

sort -t 2n /etc/passwd rootx01Super-User/
/sbin/sh daemonx11/ binx22/usr/bin sy
sx33/ admx44Admin/var/adm uucpx55u
ucp Admin/usr/lib/uucp nuucpx99uucp
Admin/var/spool/uucppublic/usr/lib/uucp/uucico l
istenx374Network Admin/usr/net/nls lpx718
Line Printer Admin/usr/spool/lp oracle10167
DBA Account/export/home/oracle/bin/csh webuser
102102Web User/export/home/webuser/bin/csh y
x6000160001Nobody/
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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
• uniqs definition of duplicated lines are
  consecutive-occurring lines that match exactly

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uniq (continue.)

• The d option is used to list duplicate lines
• Example

• cat students
• Sue
• Vara
• Elvis
• Luis
• Eliza
• Ash
• Ash
• uniq students
• Sue
• Vara
• Elvis
• Luis
• Eliza
• Ash

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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