Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: sed add space X times
Top Forums Shell Programming and Scripting sed add space X times Post 302932789 by bakunin on Saturday 24th of January 2015 03:53:21 PM
Old 01-24-2015
Quote:
Originally Posted by holyearth
I want to add X ($VARIABLE) number of spaces (which comes from RANDOM)

i.e.
VARIABLE='14'
then it will do:
Code:
sed 's/$/              /'

In short: this is not possible. The reason is that regular expressions have certain limitations and this is one of them.

If you are interested in a general and very scientific explanation of why this is so: regular expressions are of the same expressive power as regular languages, which themselves are Type-3 languages in the Chomsky-Schützenberger hierarchy. (Look up "Chomsky hierarchy" and "regular language" in Wikipedia or the net for more detail.) An expression of the form <expression> times variable would need a so-called backreference, which is not possible in a regular language because it would not be context-free any more. See the Pumping Lemma, which can be used to prove this.

Having said this: you already got some workarounds of one or the other form. Just be aware that everything you can achieve is more or less clever workarounds for the mentioned limitation.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
wisecracker
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

sed X amount of times - X is dynamic

I'm trying to make a bash shell script that will allow a user to modify another file based on input they give. Maybe someone can see what I'm doing wrong here. I'm still pretty new at this... Let's say my temp file contains this: 0 1 HELLO 3 4 And here's the code: old=(0 1 3 4) new=(zero... (2 Replies)
Discussion started by: Loriel
2 Replies

2. Shell Programming and Scripting

Awk script to add times.

Hey, Im trying to format the last command to tell me just the user names, logins, and the time that they were logged in. So far I got the users logins using a loop that counts the amount of times a user logged in but im not sure how to start the time array. The time im trying to use is the last... (2 Replies)
Discussion started by: Trilogie
2 Replies

3. Shell Programming and Scripting

How to print first two words two times using SED...

I have string as and I want to print first two words as output. (3 Replies)
Discussion started by: Diggi
3 Replies

4. Shell Programming and Scripting

Add white space to the end of a line with sed

Im trying to add 5 blank spaces to the end of each line in a file in a sed script. I can figure out who o put the spaces pretty much anywhere else but at the end. thanks Karl (7 Replies)
Discussion started by: karlanderson
7 Replies

5. Shell Programming and Scripting

Add missing times

Not sure about the title if someone has a better name for it please lemme know and I will edit the title. I have several (10+ files) which look something like: File 1: 12/28/2009 04:0 8 12/28/2009 04:4 4 12/28/2009 05:0 4 . . . File 2: 12/28/2009 04:1 7 12/28/2009 04:2 3... (2 Replies)
Discussion started by: jstrangfeld
2 Replies

6. UNIX for Advanced & Expert Users

Sed - add text to start of line if 1st char anything but space

Problem: I have a lot of files, the files first line should always have 4 spaces before any text. Occasionally some of the files will miss the leading spaces and it's a problem. This is only in the first line. So if there are 4 spaces then text, do nothing. If there are not 4 spaces, add 4... (2 Replies)
Discussion started by: Vryali
2 Replies

7. Shell Programming and Scripting

Sed or Awk for lines between two strings multiple times and keep the last one

Hi, I am trying to get lines between the last occurrences of two patterns. I have files that have several occurrences of “Standard” and “Visual”. I will like to get the lines between “Standard” and “Visual” but I only want to retain only the last one e.g. Standard Some words Some words Some... (4 Replies)
Discussion started by: damanidada
4 Replies

8. Shell Programming and Scripting

Sed replace using same pattern repeating multiple times in a line

Sed replace using same pattern repeating multiple times in a line I have text like below in a file: I am trying to replace the above line to following How can I acheive this? I am able to do it if the occurrence is for 1 time: But If I try like below I am getting like this: I have to... (4 Replies)
Discussion started by: sol_nov
4 Replies

9. Shell Programming and Scripting

Awk/sed - add space between dot and letter

I need to change . into . so that e.g. A.Jbecomes A. JI have tried sed 's/\./\.\ /g' but that didn't work. (9 Replies)
Discussion started by: locoroco
9 Replies

10. Shell Programming and Scripting

sed command to replace one value which occurs multiple times

Hi, My Input File : "MN.1.2.1.2.14.1.1" := "MN_13_TM_4" ( 000000110110100100110001111110110110101110101001100111110100011010110111001 ) "MOS.1.2.1.2.13.6.2" := "MOS_13_TM_4" ( 000000110110100100110001111110110110101110101001100111110100011010110111001 ) Like above template,I have... (4 Replies)
Discussion started by: Preeti Chandra
4 Replies

LEARN ABOUT CENTOS

paps

PAPS(1) 						      General Commands Manual							   PAPS(1)

NAME

       paps - UTF-8 to PostScript converter using Pango

SYNOPSIS

       paps [options] files...

DESCRIPTION

       paps reads a UTF-8 encoded file and generates a PostScript language rendering of the file. The rendering is done by creating outline curves
       through the pango ft2 backend.

OPTIONS

       These programs follow the usual GNU command line syntax, with long options starting with  two  dashes  (`-').   A  summary  of  options	is
       included below.

       --landscape
	      Landscape output. Default is portrait.

       --columns=cl
	      Number of columns output. Default is 1.

       --font=desc
	      Set the font description. Default is Monospace 12.

       --rtl  Do rtl layout.

       --paper ps
	      Choose paper size. Known paper sizes are legal, letter, a4. Default is A4.

       --bottom-margin=bm
	      Set bottom margin in postscript points (1/72 inch). Default is 36.

       --top-margin=tm
	      Set top margin. Default is 36.

       --left-margin=lm
	      Set left margin. Default is 36.

       --right-margin=rm
	      Set right margin. Default is 36.

       --help Show summary of options.

       --header
	      Draw page header for each page.

       --markup
	      Interpret the text as pango markup.

       --encoding=ENCODING
	      Assume the documentation encoding is ENCODING.

       --lpi  Set the lines per inch. This determines the line spacing.

       --cpi  Set the characters per inch. This is an alternative method of specifying the font size.

       --stretch-chars
	      Indicates  that  characters  should be stretched in the y-direction to fill up their vertical space. This is similar to the texttops
	      behaviour.

AUTHOR

       paps was written by Dov Grobgeld <dov.grobgeld@gmail.com>.

       This manual page was written by Lior Kaplan <kaplan@debian.org>, for the Debian project (but may be used by others).

								  April  17, 2006							   PAPS(1)
All times are GMT -4. The time now is 02:43 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy