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Full Discussion: Good sed Book?
Top Forums Shell Programming and Scripting Good sed Book? Post 302730357 by DGPickett on Monday 12th of November 2012 04:55:26 PM
Old 11-12-2012
Well, sed is so simple, I taught myself. I find there are two flavors of script, loopers and filters. Loopers read most or all lines but the first using N, so they can see multiple lines in the buffer, and loop using branch features. Filters just do things on each line, as one mainly thinks of sed doing.

Awk has variables, arrays, hash tables, a sense of fields and records divorced from the line feed, which sed lacks, but is complex enough that one might just as well learn PERL, which is more able and orthogonal. Adding to the pifalls of awk is that there was an old awk and new awk, sometimes nawk, so examples may vary in dialect.

Most of sed is also usable in grep, vi, ex, and on the command line of ksh and bash when in 'set -o vi' mode, my favorite. I started on regex line editors with qedx in MULTICs, then used them in GCOS with University of Waterloo FRED the friendly editor, before I arrived in UNIX/vi land.

Regex are extended in several flavors, so what works in sed is more than basic grep but less that egrep/"grep -E" and that is different from awk.

You can make executable pure sed or awk files if the first line is "#!/bin/sed -f". I usually write sed right on the command line, barefoot inside ', like this extra blank (all white space) line remover, a classic looper (\t is a real tab, [f a real form feed):
Code:
sed '
  s/[ \t\f]*$//
  :loop
  $b
  N
  s/[ \t\f]*$//
  s/^\n$//
  t loop
  P
  s/.*\n//
  t loop
 '

The '$b' ensures that N is not run at EOF, losing a line on some early, defective sed implementations. Early proprietary sed was fixed buffer but faster than GNU and later sed's with realloc()-able indirect buffers. I often kept both around for script compatibility, renaming GNU sed 'gsed'. In one app, I turned whole pages into lines using 'tr' to swap line feeds and form feeds, so I could mark up the pages in sed to insert them into the database as big strings. I am not shy about running multiple sed's in a row, as looper sed and filter sed are not friends, and get some multiprocessing in the deal:
Code:
sed '
  s/[ \t\f]*$//
 ' | sed '
  :loop
  $b
  N
  s/^\n$//
  t loop
  P
  s/.*\n//
  t loop
 '

 

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LEARN ABOUT SUSE

nwbpset

NWBPSET(1)							      nwbpset								NWBPSET(1)

NAME

       nwbpset - Create a bindery property or set its value

SYNOPSIS

       nwbpset [ -h ] [ -S server ] [ -U user name ] [ -P password | -n ] [ -C ]

DESCRIPTION

       nwbpset Reads a property specification from the standard input and creates and sets the corresponding property. The format is determined by
       the output of 'nwbpvalues -c'. nwbpset will hopefully become an important part of the bindery management suite of ncpfs, together with

       As another example, look at the following command line:

	 nwbpvalues -t 1 -o supervisor -p user_defaults -c |
	 sed '2s/.*/ME/'|
	 sed '3s/.*/LOGIN_CONTROL/'|
	 nwbpset

       With this command, the property user_defaults of the user object 'supervisor' is copied into the property login_control of the user  object
       'me'.

	 nwbpvalues -t 1 -o me -p login_control -c |
	 sed '9s/.*/ff/'|
	 nwbpset

       This command disables the user object me.

       Feel free to contribute other examples!

       nwbpset looks up the file $HOME/.nwclient to find a file server, a user name and possibly a password. See nwclient(5) for more information.
       Please note that the access permissions of $HOME/.nwclient MUST be 600 for security reasons.

OPTIONS

       -h
	  -h is used to print out a short help text.

       -S server
	  server is the name of the server you want to use.

       -U user
	  user is the user name to use for login.

       -P password
	  password is the password to use for login. If neither -n nor -P are given, and the user has no open connection to  the  server,  nwbpset
	  prompts for a password.

       -n
	  -n should be given if no password is required for the login.

       -C
	  By default, passwords are converted to uppercase before they are sent to the server, because most servers require this. You can turn off
	  this conversion by -C.

AUTHORS

       nwbpset was written by Volker Lendecke. See the Changes file of ncpfs for other contributors.

nwbpset 							     8/7/1996								NWBPSET(1)
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