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Full Discussion: Doubt in SED command
Top Forums UNIX for Advanced & Expert Users Doubt in SED command Post 302168798 by sb008 on Tuesday 19th of February 2008 01:20:11 PM
Old 02-19-2008
Quote:
Originally Posted by gksenthilkumar
PLEASE EXPLANIN ME...
sed 's~\(.*\)\(<name>\)\(.*\)\(</name>\)\(.*\)~\2\3\4~'

this is the format
<start><name>123<\name><addr>BAC<\addr><loc>sfo<\loc></start>
.* zero or more random characters
<name> literally the string
</name> literally the string

Find lines with "<name>" and "</name>", where "<name>" can preceded by any amount of characters, "</name>" can be followed by any amount of characters, and there can be any amount of characters in between "<name>" and "</name>"

\(.....\) whatever is found put in a buffer, subsequent \(.....\) means put in next buffer.

1st \(.*\) will match "<start>" and this string will be placed in buffer 1
\(<name>\) will match "<name>" and this string will be placed in buffer 2
2nd \(.*\) will match "123" and this string will be placed in buffer 3
\(</name>\) will match "</name>" and this string will be placed in buffer 4
\(.*\) will match "<addr>BAC<\addr><loc>sfo<\loc></start>" and this string will be placed in buffer 5.

"~" is used in the sed instead of "/" so the "/" in "</name>" doesnt need to be escaped.

If a line is found which matches the patterns, replace them by what ever is in buffer 2,3 and 4.

So based on the string given:
<start><name>123<\name><addr>BAC<\addr><loc>sfo<\loc></start>

The result of the sed command:
sed 's~\(.*\)\(<name>\)\(.*\)\(</name>\)\(.*\)~\2\3\4~'

will be:
<name>123<\name>

Shorter:
sed 's~.*\(<name>\)\(.*\)\(</name>\).*~\1\2\3~'

With "/" instead of "~":
sed 's/.*\(<name>\)\(.*\)\(<\/name>\).*/\1\2\3/'
 

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LEARN ABOUT OSF1

xmtextfindstring

XmTextFindString(3X)													      XmTextFindString(3X)

NAME

       XmTextFindString - A Text function that finds the beginning position of a text string

SYNOPSIS

       #include <Xm/Xm.h>

       Boolean XmTextFindString (widget, start, string, direction, position)
	       Widget widget;
	       XmTextPosition start;
	       char *string;
	       XmTextDirection direction;
	       XmTextPosition *position;

DESCRIPTION

       XmTextFindString locates the beginning position of a specified text string.  This routine searches forward or backward for the first occur-
       rence of the string starting from the given start position.  If it finds a match, the function returns the position of the first  character
       of  the	string	in  position.  Specifies the Text widget ID.  Specifies the character position from which the search proceeds.	This is an
       integer number of characters from the beginning of the text buffer.  The first character position  is  0.   Specifies  the  search  string.
       Indicates  the search direction.  It is relative to the primary direction of the text.  The possible values are: The search proceeds toward
       the end of the text buffer.  The search proceeds toward the beginning of the text buffer.  Specifies the pointer in which the first charac-
       ter position of the string match is returned.  This is an integer number of characters from the beginning of the buffer.  The first charac-
       ter position is 0.  If the function returns False, this value is undefined.

       For a complete definition of Text and its associated resources, see XmText(3X).

RETURN VALUE

       Returns True if a string match is found; otherwise, returns False.

SEE ALSO

       XmText(3X), XmTextFindStringWcs(3X)

															      XmTextFindString(3X)
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