Unix Lecture 2 Special Characters for Searches

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Unix Lecture 2Special Characters for Searches
SubstitutionsShell Scripts

• Hana Filip

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Create a Large Practice File

• 1, copy RETURN
• In the visual editor Command Mode
• Copy all the lines of the file

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Slash-Search Command

• /he RETURN
• Matches all he strings of characters
• shepherd
• the
• their
• mother

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Beginnings and Endings of Words

• /\lthe\gt RETURN
• \lt beginning of a word
• \gt ending of a word

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Beginning of a Line

• / RETURN
• Press the n several times and see what happens
• /The RETURN

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End of Line Character

• /werewolf RETURN

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Finding Blank Lines

• / RETURN

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Upper and Lower Case Searches

• /Fformatting RETURN

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Locating a Range of Characters

• /0-9 RETURN
• /A-Z RETURN
• /a-z RETURN

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Excluding Characters from a Search

• /0-9 RETURN
• /A-Z RETURN
• /a-z RETURN

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Several Identifiers

• /0-9A-Za-z RETURN
• Will go to those characters not numbers, nor
  upper or lower case letters
• Scope of negation (0-9A-Za-z)

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Any SINGLE Character

• /. RETURN
• /\lt.he\gt RETURN
• Finds the next example of a three-letter word
  ending in he

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Repeated Characters

• /ol RETURN
• Finds all words that have an o followed by zero
  or more ls
• Kleene star, means any possible number
  (including zero) of the previous character
• Locate sets of two or more identical characters
  x
• xxx

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Any Number of Any Character

• /s.s RETURN
• Locates the next line containing an s followed
  by any sequence of characters followed by s

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Backslash the Kryptonite of Special Characters

• /\. RETURN
• Locates the next occurrence of a dot
• /\. RETURN
• Locates the next line that starts with a dot

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Exercise

• What command would locate the next instance of a
  sequence of characters starting with psy and
  ending with y or t?
• /\ltpsy.yt\gt RETURN

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Global Searches and Substitutions

• Substitutions within the current line
• /the RETURN
• Locates the next line containing the word the
  (the same as /the RETURN) and makes that line
  the current line
• s/the/some RETURN
• Locates the next occurrence of the word the
  on the current line and substitutes it with
  some,otherwise fails (if the is NOT on the
  current line)

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Global Searches and Substitutions

• Substitution for the Next Occurrence
• /the/s/the/some RETURN
• /the find the next line containing the word
  the and make that line the current line
• /s/the/some substitute for the word the the
  word some

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Global Searches and Substitutions

• The Easier Way to Substitute for the Next
  Occurrence
• /the/s/the/some RETURN
• /the/s//some RETURN
• // the last string of characters mentioned

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Global Searches and Substitutions

• Substitution on All Lines
• g/the/s//mutate RETURN
• g global, all lines
• Search for and substitute the first occurrence
  of the specified word in every line

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Global Searches and Substitutions

• Substitution for All Occurrences
• g/the/s//mutate/g RETURN
• g global, all lines
• Search for and substitute all the occurrences of
  the specified word in every line

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Exercise

• Substitute all the occurrences of the word and
  with or
• g/\ltand\gt/s//or/g RETURN
• g/spaceandspace/s//spaceorspace/g RETURN

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Summary of Substitution Commands

• /word/s//newword RETURN
• Changes the first occurrence in first line
• g/word/s//newword RETURN
• Changes the first occurrence in all lines
• g/word/s//newword/g RETURN
• Changes all occurrences in all lines

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Global Searches and Substitutions

• Print a Display of Identified Lines
• g/Formatted/p RETURN

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Global Searches and Substitutions

• Removing Multiple Spaces
• g/3spaces/s//1space/g RETURN
• Substitutes 2 or more spaces with 1 space
• g/3spaces/s//1space/g RETURN
• g/3spaces/s//1space/g RETURN

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Global Searches and Substitutions

• Removing Blank Lines
• g//d RETURN

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Global Searches and Substitutions

• Adding to Words
• g/cover\gt/s//ing/p RETURN
• the last pattern found
• p prints the changed line(s) on the terminal
• g/\ltterre./s//extra/p RETURN
• extra is prefixed to terrestrial

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Global Searches and Substitutions

• Editor Scripts
• vi script1 RETURN
• g/0-9/d
• g/William/s//Bill/g
• wq
• Your file should contain the above three lines
• wq is the command to write changes made to the
  file into the memory of UNIX and return to the
  Shell

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Global Searches and Substitutions

• Editor Scripts
• Create a file entitled clinton
• William Jefferson Clinton (born William Jefferson
• Blythe III1 on August 19, 1946)
• was the 42nd
• President of the United States,
• serving from 1993 to 2001.

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Global Searches and Substitutions

• Editor Scripts
• ex clinton lt script1 RETURN
• ex execute
• Output
• Wills Jefferson Clinton (born Wills Jefferson
• President of the United States,

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Global Searches and Substitutions

• Editor Scripts
• A clean-Up Script
• vi script2 RETURN
• g//d
• g/ /s/// 2 spaces
• g/ /s/// 2 spaces
• g/ /s// /g 3 spaces 1 space
• wq

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Summary Meta-Characters

• Command Function
• match beginning of line
• match end of line
• . match any single character
• match any number of occurrences of previous
  character (also 0)
• match any character (or range of characters
  enclosed within the
• brackets
• match any character (or range of characters
  NOT enclosed within
• the brackets
• \lt match beginning of a
  word or a phrase
• gt\ match ending of a
  word or a phrase
• replace target
  character(s) with last character pattern
  encountered
• \ remove magic of Special
  Characters (Kryptonite)
• / / match last pattern in search

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SummaryRegular Characters

• Command Function
• g at the beginning of a search all lines in
  the file
• at end of a search all cases of pattern within
  specified lines
• s substitute for last pattern found
• p at end of a search display pattern found on
  your screen
• d at end of a search delete all lines in which
  pattern is found