Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Understanding sed
Top Forums Shell Programming and Scripting Understanding sed Post 302774419 by gary_w on Friday 1st of March 2013 10:20:39 PM
Old 03-01-2013
An attempt to further explain the regular expression, with an ulterior motive of setting up for a question.

Given:
Code:
sed 's/^\([^:]*\):[^:]:/\1::/'

search for a pattern in the string matching:
Code:
^    = start of the line
\(   = Start of first remembered pattern
[^:] = followed by any character that is not a :
*    = followed by any number of the previous character class
       (characters that are not colons)
\)   = end of first remembered pattern
:    = followed by a colon
[^:] = followed by any character that is not a colon
:    = followed by a colon

<describes the first 2 fields, along with their seperators>

Replace with:
Code:
\1   = the first remembered pattern (the first field)
::   = followed by 2 literal colons

In other words, replace the first 2 colon separated fields
with the first field and 2 colons (deletes the 2nd field).

Question: if this sed command was in a script, could it be commented like I did above in the code? Can a sed regex be multi-line with comments?

One could also do:
Code:
s/:[^:]*:/::/

 

9 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

need further understanding of init.d

I needt o know how what init.d does and how it knows which dameons/applications to turn off and how to restart the applications after reboot. any OS - solaris/hp-ux (1 Reply)
Discussion started by: jigarlakhani
1 Replies

2. Shell Programming and Scripting

understanding the sed command

Guys, I am trying to understand the sed command here. adx001 $ a=/clocal/dctrdata/user/dctrdat1/trdroot/recouncil adx001 $ b=`echo $a | sed 's/\//\\\\\//g'` adx001 $ echo $b \/clocal\/dctrdata\/user\/dctrdat1\/trdroot\/recouncil The sed command i took it from the script. Please... (3 Replies)
Discussion started by: mac4rfree
3 Replies

3. UNIX for Dummies Questions & Answers

Help understanding sed

I am trying to create a basic script that converts an Oracle script into a Sybase script. The only things im changing are Datatypes and the to_char and to_date functions. I am not really 100% sure of the way it works. I have tried running the functions through a loop to replace each word line... (6 Replies)
Discussion started by: Makaer
6 Replies

4. Shell Programming and Scripting

need help understanding mv

I just started shell coding and I'm a bit confused on how 'mv' works can someone explain to me how it works and if i did this correctly. Thanks. echo "Enter Name of the first file:" read file1 #echo $file1 if ; then echo "Sorry, file does not exist." exit 1 ... (16 Replies)
Discussion started by: taiL
16 Replies

5. UNIX for Dummies Questions & Answers

understanding {%/*}/

Hi Gurus: I am trying to understand the following line of code.I did enough of googling to understand but no luck.Please help me understand the follow chunk of code: X=$0 MOD=${X%/*}/env.ksh X is the current script from which I am trying to execute. Say if X=test.ksh $MOD is echoing :... (3 Replies)
Discussion started by: vemana
3 Replies

6. UNIX for Dummies Questions & Answers

understanding sed command

Hi Friends, I need a small help in understanding the below sed command. $ cat t4.txt 1 root 1 58 0 888K 368K sleep 4:06 0.00% init 1 root 1 58 0 888K 368K sleep 4:06 0.00% init last $ sed 's/*$//' t4.txt 1 root 1 58 0 888K ... (3 Replies)
Discussion started by: forroughuse
3 Replies

7. Shell Programming and Scripting

help understanding regex with grep & sed

I have the following line of code that works wonders. I just don't completely understand it as I am just starting to learn regex. Can you help me understand exactly what is happening here? find . -type f | grep -v '^\.$' | sed 's!\.\/!!' (4 Replies)
Discussion started by: trogdortheburni
4 Replies

8. Shell Programming and Scripting

Need your help in understanding this

Hi, I found this in a script and I would like to know how this works Code is here: # var1=PART1_PART2 # var2=${var1##*_} # echo $var2 PART2 I'm wondering how ##* makes the Shell to understand to pick up the last value from the given. (2 Replies)
Discussion started by: sathyaonnuix
2 Replies

9. Shell Programming and Scripting

Need Quick help on Understanding sed Regex

Hi Guys, Could you please kindly explain what exactly the below SED command will do ? I am quite confused and i assumed that, sed 's/*$/ /' 1. It will remove tab and extra spaces .. with single space. The issue is if it is removing tab then it should be Î right .. please assist.... (3 Replies)
Discussion started by: Nandy
3 Replies

LEARN ABOUT SUSE

irsend

IRSEND(1)								FSF								 IRSEND(1)

NAME

       irsend - basic LIRC program to send infra-red commands

SYNOPSIS

       irsend [options] DIRECTIVE REMOTE CODE [CODE...]

DESCRIPTION

       Asks the lircd daemon to send one or more CIR (Consumer Infra-Red) commands. This is intended for remote control of electronic devices such
       as TV boxes, HiFi sets, etc.

       DIRECTIVE can be:
	  SEND_ONCE	    - send CODE [CODE ...] once
	  SEND_START	    - start repeating CODE
	  SEND_STOP	    - stop repeating CODE
	  LIST		    - list configured remote items
	  SET_TRANSMITTERS  - set transmitters NUM [NUM ...]
	  SIMULATE	    - simulate IR event

       REMOTE is the name of a remote, as described in the lircd configuration file.

       CODE is the name of a remote control key of REMOTE, as it appears in the lircd configuration file.

       NUM is the transmitter number of the hardware device.

       For the LIST DIRECTIVE, REMOTE and/or CODE can be empty:

	  LIST	 ""    ""   - list all configured remote names
	  LIST REMOTE  ""   - list all codes of REMOTE
	  LIST REMOTE CODE  - list only CODE of REMOTE

       The SIMULATE command only works if it has been explicitly enabled in lircd.

       -h --help
	      display usage summary

       -v --version
	      display version

       -d --device
	      use given lircd socket [/var/run/lirc/lircd]

       -a --address=host[:port]
	      connect to lircd at this address

       -# --count=n
	      send command n times

EXAMPLES

	  irsend LIST DenonTuner ""
	  irsend SEND_ONCE  DenonTuner PROG-SCAN
	  irsend SEND_ONCE  OnkyoAmpli VOL-UP VOL-UP VOL-UP VOL-UP
	  irsend SEND_START OnkyoAmpli VOL-DOWN ; sleep 3
	  irsend SEND_STOP  OnkyoAmpli VOL-DOWN
	  irsend SET_TRANSMITTERS 1
	  irsend SET_TRANSMITTERS 1 3 4
	  irsend SIMULATE "0000000000000476 00 OK TECHNISAT_ST3004S"

FILES

       /etc/lirc/lircd.conf
	      Default lircd configuration file.  It should contain all the remotes, their infra-red codes and the corresponding timing	and  wave-
	      form details.

DIAGNOSTICS

       If lircd is not running (or /var/run/lirc/lircd lacks write permissions) irsend aborts with the following diagnostics:
       "irsend: could not connect to socket"
       "irsend: Connection refused" (or "Permission denied").

SEE ALSO

       The documentation for lirc is maintained as html pages. They are located under html/ in the documentation directory.

       lircd(8), mode2(1), smode2(1), xmode2(1), irrecord(1), irw(1), http://www.lirc.org.

irsend 0.8.7pre1						     May 2010								 IRSEND(1)
All times are GMT -4. The time now is 08:25 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy