January 23, 2007Spring 20071 Unix Lecture 2 Special Characters for Searches & Substitutions Shell...

January 23, 2007 Spring 2007 1

Unix Lecture 2Special Characters for Searches & Substitutions

Shell Scripts

Hana Filip


Create a Large Practice File

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


Slash-Search Command

/he [RETURN]– Matches all he strings of characters – shepherd – the – their– mother


Beginnings and Endings of Words

/\<he\> [RETURN]

\< beginning of a word

\> ending of a word


Beginning of a Line

/^ [RETURN]

Press the n several times and see what happens

/^The [RETURN]


End of Line Character

$

/werewolf$ [RETURN]


Finding Blank Lines

/^$ [RETURN]


Upper and Lower Case Searches

/[Ff]ormatting [RETURN]


Locating a Range of Characters

/[0-9] [RETURN]

/[A-Z] [RETURN]

/[a-z] [RETURN]


Excluding Characters from a Search

/[^0-9] [RETURN]

/[^A-Z] [RETURN]

/[^a-z] [RETURN]


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)


Any SINGLE Character

/. [RETURN]

/\<.he\> [RETURN]

Finds the next example of a three-letter word ending in he


Repeated Characters

/ol* [RETURN]– Finds all words that have an o followed by zero or

more l’s

– * Kleene star, means “any possible number (including zero) of the previous character”

– Locate sets of two or more identical characters x:

xxx*


Any Number of Any Character

/s.*s [RETURN]

Locates the next line containing an s followed by any sequence of characters followed by s


Backslash the Kryptonite of Special

Characters

/\. [RETURN]

Locates the next occurrence of a dot

/^\. [RETURN]

Locates the next line that starts with a dot


Exercise

What command would locate the next instance of a sequence of characters starting with psy and ending with y or t?

/\<psy.*[yt]\> [RETURN]


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)



• 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”



The Easier Way to Substitute for the Next Occurrence

:/the/s/the/some [RETURN]

:/the/s//some [RETURN]// “the last string of characters mentioned”



• 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



• 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


Exercise

Substitute all the occurrences of the word and with or

:g/\<and\>/s//or/g [RETURN]

:g/spaceandspace/s//spaceorspace/g [RETURN]


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



Print a Display of Identified Lines

:g/Formatted/p [RETURN]



• 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]



• Removing Blank Lines

:g/^$/d [RETURN]



Adding to Words

:g/cover\>/s//&ing/p [RETURN]& the last pattern found

p prints the changed line(s) on the terminal

:g/\<terre.*/s//extra&/p [RETURN]

extra is prefixed to terrestrial



Editor Scripts% vi script1 [RETURN]g/[0-9]/dg/William/s//Bill/gwq

Your file should contain the above three lineswq is the command to write changes made to the file into the memory of UNIX and return to the Shell



Editor ScriptsCreate a file entitled clinton

William Jefferson Clinton (born William Jefferson

Blythe III[1] on August 19, 1946)

was the 42nd

President of the United States,

serving from 1993 to 2001.



Editor Scripts

% ex clinton < script1 [RETURN]

ex execute

Output:Wills Jefferson Clinton (born Wills JeffersonPresident of the United States,



Editor ScriptsA clean-Up Script% vi script2 [RETURN]g/^$/dg/^ */s/// 2 spacesg/ *$/s/// 2 spacesg/ */s// /g 3 spaces 1 spacewq


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

\< match beginning of a word or a phrase>\ 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


SummaryRegular Characters

Command Functiong 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

January 23, 2007Spring 20071 Unix Lecture 2 Special Characters for Searches & Substitutions Shell...

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