Sponsored Content
Top Forums Shell Programming and Scripting Using sed to execute multiple commands Post 302831323 by DGPickett on Wednesday 10th of July 2013 04:51:59 PM
Old 07-10-2013
Here is a looper to remove more than one consecutive blank lines, which illustrates the concept:
Code:
sed '
  :loop
  $b
  N
  s/^\n$//
  t loop
  P
  s/.*\n//
  b loop
 '

I put my sed script on its own lines for clarity. If you want to check for lines with only spaces and tabs, that scrubbing can be done upstream in one line or inserted here as two lines. That is why I say sed loopers are usually best kept separate from non-loopers. There is no single place to filter and translate single lines in a looper without redundant processing, like substituting on each line twice.

Narrative:
  1. Create a branch target,
  2. if last line branch to end of script (print buffer and exit) as $N usually tosses the last line,
  3. get the next line on end of buffer as '\nLine_2',
  4. if both lines are empty, remove one,
  5. if line was removed branch back to loop,
  6. print the first line,
  7. remove the first line and
  8. branch back to loop.

Last edited by DGPickett; 07-10-2013 at 06:00 PM..
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

multiple sed commands

hello! I have a few sed commands sed '/^$/d' < $1 > tmp.t sed '/^ \{3,\}/d' < tmp.t > tmp1.txt ..... how can I write them in a single line? sed '/^$/d' < $1 > | '/^ \{3,\}/d' < $1 > tmp1.txt any idea? thanks. (5 Replies)
Discussion started by: george_
5 Replies

2. Shell Programming and Scripting

how do i get my script to execute multiple commands?

New to shell scripting. I can't get my script to execute multiple commands. Here's the code. It's a menu script. #!/bin/ksh clear print "SDE MENU" PS3="SDE MENU, enter choice:" select clean_menu in "tasdedev instance 5151" "orkindev instance 5155" "tasdetst instance 5157" "orkinsys... (1 Reply)
Discussion started by: hvincent
1 Replies

3. Shell Programming and Scripting

Can Xargs execute multiple commands of evry input file

Hello , I am trying to print the footer of evry file in the given directory with xargs command like follows ls -1 | xargs -I {} gzcat {} | tail -1 now problem with this is only last file foooter is getting printed as " | tail -1 " is getting executed for the last file. I know this can... (4 Replies)
Discussion started by: nilesrex
4 Replies

4. Shell Programming and Scripting

Execute multiple commands in a find

I am checking that a file is older than a reference file that I build with a touch command before processing it. If it is not old enough, I want to sleep for an hour and check again. My problem is if it is old enough to process, I want to exit when I am done, but I cannot find a way to exit... (2 Replies)
Discussion started by: prismtx
2 Replies

5. UNIX for Advanced & Expert Users

How to execute multiple unix commands in one session from java

Hi, Iam trying to code in java and wanted to run the commands in the Unix remote servers. I have the following code to run multiple GREP commands in a single session. But when i execute this, the first command executes successfully, whereas from the next line it says "Exception Occured... (1 Reply)
Discussion started by: gravi2020
1 Replies

6. UNIX for Dummies Questions & Answers

cron used to execute multiple commands

have to run multiple commands at a specified time by the user... (3 Replies)
Discussion started by: hemaa
3 Replies

7. Shell Programming and Scripting

connect to multiple servers using SSH and execute commands

Requirement: Run a shell script with below inputs file name checksum path the script should go to multiple servers (around 35) and verify the input cksum and if there is a mismatch display a simple message to the user that cksum verification failed. host details, user id /... (1 Reply)
Discussion started by: amicableperson
1 Replies

8. Shell Programming and Scripting

How to execute multiple commands in one shot?

for example: I'm greping the process where i can get the location of the file $ ps -ef | grep LLAWP | awk {'print $9'} | tail -1 /Hostname/ihs/INSTANCE2/conf/WebAgent.conf then I need to display second line of WebAgent.conf file: $ cat /Hostname/ihs/INSTANCE1/conf/WebAgent.conf | head... (2 Replies)
Discussion started by: raghur77
2 Replies

9. Shell Programming and Scripting

Ssh multiple hops to execute commands with arguments

Hi I need to write a script to ssh through several hops (e.g. HostA-HostB-HostC-HostD), where Host A does not have direct assess to HostC ; HostB cannot access HostD directly. when I ssh 3 hops and run command with arg1, arg2 and redirect the output to a file, e.g. HostA> ssh -t HostB ssh -t... (3 Replies)
Discussion started by: chiensh
3 Replies

10. UNIX for Beginners Questions & Answers

Use sed commands on multiple lines

I have a text file and i want to run 3 sed commands for the lines entered by the user using perl script. I am doing this manually till now. need some help with this The sed commands I have to use are : sed -i "s/{+//" error.txt sed -i "s/+}//" error.txt sed -i "s/\//g" error.txt... (5 Replies)
Discussion started by: utkarshkhanna44
5 Replies
SED(1)							      General Commands Manual							    SED(1)

NAME
sed - stream editor SYNOPSIS
sed [ -n ] [ -e script ] [ -f sfile ] [ file ] ... DESCRIPTION
Sed copies the named files (standard input default) to the standard output, edited according to a script of commands. The -f option causes the script to be taken from file sfile; these options accumulate. If there is just one -e option and no -f's, the flag -e may be omitted. The -n option suppresses the default output. A script consists of editing commands, one per line, of the following form: [address [, address] ] function [arguments] In normal operation sed cyclically copies a line of input into a pattern space (unless there is something left after a `D' command), applies in sequence all commands whose addresses select that pattern space, and at the end of the script copies the pattern space to the standard output (except under -n) and deletes the pattern space. An address is either a decimal number that counts input lines cumulatively across files, a `$' that addresses the last line of input, or a context address, `/regular expression/', in the style of ed(1) modified thus: The escape sequence ` ' matches a newline embedded in the pattern space. A command line with no addresses selects every pattern space. A command line with one address selects each pattern space that matches the address. A command line with two addresses selects the inclusive range from the first pattern space that matches the first address through the next pattern space that matches the second. (If the second address is a number less than or equal to the line number first selected, only one line is selected.) Thereafter the process is repeated, looking again for the first address. Editing commands can be applied only to non-selected pattern spaces by use of the negation function `!' (below). In the following list of functions the maximum number of permissible addresses for each function is indicated in parentheses. An argument denoted text consists of one or more lines, all but the last of which end with `' to hide the newline. Backslashes in text are treated like backslashes in the replacement string of an `s' command, and may be used to protect initial blanks and tabs against the stripping that is done on every script line. An argument denoted rfile or wfile must terminate the command line and must be preceded by exactly one blank. Each wfile is created before processing begins. There can be at most 10 distinct wfile arguments. (1)a text Append. Place text on the output before reading the next input line. (2)b label Branch to the `:' command bearing the label. If label is empty, branch to the end of the script. (2)c text Change. Delete the pattern space. With 0 or 1 address or at the end of a 2-address range, place text on the output. Start the next cycle. (2)d Delete the pattern space. Start the next cycle. (2)D Delete the initial segment of the pattern space through the first newline. Start the next cycle. (2)g Replace the contents of the pattern space by the contents of the hold space. (2)G Append the contents of the hold space to the pattern space. (2)h Replace the contents of the hold space by the contents of the pattern space. (2)H Append the contents of the pattern space to the hold space. (1)i text Insert. Place text on the standard output. (2)n Copy the pattern space to the standard output. Replace the pattern space with the next line of input. (2)N Append the next line of input to the pattern space with an embedded newline. (The current line number changes.) (2)p Print. Copy the pattern space to the standard output. (2)P Copy the initial segment of the pattern space through the first newline to the standard output. (1)q Quit. Branch to the end of the script. Do not start a new cycle. (2)r rfile Read the contents of rfile. Place them on the output before reading the next input line. (2)s/regular expression/replacement/flags Substitute the replacement string for instances of the regular expression in the pattern space. Any character may be used instead of `/'. For a fuller description see ed(1). Flags is zero or more of g Global. Substitute for all nonoverlapping instances of the regular expression rather than just the first one. p Print the pattern space if a replacement was made. w wfile Write. Append the pattern space to wfile if a replacement was made. (2)t label Test. Branch to the `:' command bearing the label if any substitutions have been made since the most recent reading of an input line or execution of a `t'. If label is empty, branch to the end of the script. (2)w wfile Write. Append the pattern space to wfile. (2)x Exchange the contents of the pattern and hold spaces. (2)y/string1/string2/ Transform. Replace all occurrences of characters in string1 with the corresponding character in string2. The lengths of string1 and string2 must be equal. (2)! function Don't. Apply the function (or group, if function is `{') only to lines not selected by the address(es). (0): label This command does nothing; it bears a label for `b' and `t' commands to branch to. (1)= Place the current line number on the standard output as a line. (2){ Execute the following commands through a matching `}' only when the pattern space is selected. (0) An empty command is ignored. SEE ALSO
ed(1), grep(1), awk(1), lex(1) 7th Edition April 29, 1985 SED(1)
All times are GMT -4. The time now is 04:29 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy