Linux in a Nutshell, Fifth Edition

t | 767

sed

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

\U Uppercase the replacement text until a terminating \E or \L.

\u Uppercase the following character only.

\E Terminate case conversion from \L or \U.

Examples

Here are some short, commented scripts:

# Change third and fourth quote to ( and ):

/function/{

s/"/)/4

s/"/(/3

}

# Remove all quotes on a given line:

/Title/s/"//g

# Remove first colon and all quotes; print resulting

lines:

s/://p

s/"//gp

# Change first "if" but leave "ifdef" alone:

/ifdef/!s/if/ if/

t

[address1[,address2]]t [label]

Test if successful substitutions have been made on addressed lines,

and if so, branch to the line marked by :label. (See b and

:.) If label

is not specified, control branches to the bottom of the script. The t

command is like a case statement in the C programming language

or the various shell programming languages. You test each case;

when it’s true, you exit the construct.

Example

Suppose you want to fill empty fields of a database. You have this:

ID: 1 Name: greg Rate: 45

ID: 2 Name: dale

ID: 3

You want this:

ID: 1 Name: greg Rate: 45 Phone: ??

ID: 2 Name: dale Rate: ?? Phone: ??

ID: 3 Name: ???? Rate: ?? Phone: ??

You need to test the number of fields already there. Here’s the

script (fields are tab-separated):

#n

/ID/{

s/ID: .* Name: .* Rate: .*/& Phone: ??/p

t

s/ID: .* Name: .*/& Rate: ?? Phone: ??/p

t

s/ID: .*/& ...