Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: How to replace all but the first 3 characters with sed?
Top Forums Shell Programming and Scripting How to replace all but the first 3 characters with sed? Post 302934793 by Scrutinizer on Tuesday 10th of February 2015 09:37:49 PM
Old 02-10-2015
Quote:
Originally Posted by DGPickett
I hate sed loops for one byte change per loop, so you can split the lines and then rejoin them[..]
Quote:
Originally Posted by RudiC
Point taken! I don't really like pipe organs, so tried a no loop no pipe solution[..]
Did a small test and indeed, those 1 character loops are expensive.
It turns the awk solutions appear to be fastest.
Code:
$ time sed -e :a -e 's/\(...\)[^*]/\1*/;ta' file > /dev/null

real	0m0.114s
user	0m0.110s
sys	0m0.003s

$ time { sed '
  s/^.\{0,3\}/&\
/
' file | sed '
  $q
  N
  P
  s/.*\n//
  s/./*/g
'|sed '
  $q
  N
  s/\n//
' ;} > /dev/null

real	0m0.015s
user	0m0.015s
sys	0m0.006s

$ time sed 'h;s/\(...\).*/\1/;x;s/^...//;s/./*/g;H;x;s/\n//' file > /dev/null

real	0m0.018s
user	0m0.013s
sys	0m0.002s

$ time perl -pe 's/(?<=...)./*/g' file >/dev/null

real	0m0.030s
user	0m0.022s
sys	0m0.005s

$ time awk '{x=substr($0,N+1); gsub(".","*",x); print substr($0,1,N) x}' N=3 file > /dev/null

real	0m0.010s
user	0m0.007s
sys	0m0.002s

$ time gsed "s/./*/4g" file > /dev/null

real	0m0.022s
user	0m0.018s
sys	0m0.002s

time awk -F'^...' '{a=$2; gsub(/./,"*",a); print substr($0,1,3) a}' file > /dev/null

real	0m0.009s
user	0m0.006s
sys	0m0.003s

Last edited by Scrutinizer; 02-10-2015 at 11:13 PM.. Reason: Some sed/awk times were GNU sed/awk, rather than BSD sed/awk. Correct it
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

how to replace control characters using sed?

How can I use sed to replace a ctrl character such as 'new line' (\0a) to something else? Or any other good command can do this job? Thanks, Hillxy (5 Replies)
Discussion started by: hillxy
5 Replies

2. Shell Programming and Scripting

Sed replace characters not equal to an expression

Hi all, Suppose I have a file with the contents below, and I only want to print words %S_ then | sort -u. ------------------------------ The %S_MSG that starts with '%.*s' is too long. Maximum length is %d. The %S_MSG name '%.*s' contains more than the maximum number of prefixes. The... (5 Replies)
Discussion started by: poldo
5 Replies

3. Shell Programming and Scripting

Using sed to replace special characters

Hi everyone I have file1 contains: '7832' ' 8765 6543 I want a sed command that will format as: '7832' , '8765' , '6543' I tried sed -e s/\'//g -e 's/^*//;s/*$//' file1 > file2 sed -e :a -e '$!N; s/\n/ /; ta' file2 which gives: 7832 8765 6543 I need some help to continue with... (5 Replies)
Discussion started by: nimo
5 Replies

4. Shell Programming and Scripting

Bash: using SED, trying to replace some characters except first or last line

Hi, I require to replace 2 items: 1. replace start of all lines in a file with ' except the first line 2. replace end of all lines in a file with '||chr( except last line I am able to do the entire file using sed -e s/^/\'/g -e s/$/\'\|\|chr\(/g "$file" > newfile.txt but am not yet able... (0 Replies)
Discussion started by: Chella15
0 Replies

5. UNIX for Dummies Questions & Answers

Bash: using SED, trying to replace some characters except first or last line

Hi, I require to replace 2 items: 1. replace start of all lines in a file with ' except the first line 2. replace end of all lines in a file with '||chr( except last line I am able to do the entire file using sed -e s/^/\'/g -e s/$/\'\|\|chr\(/g "$file" > newfile.txt but am not yet... (3 Replies)
Discussion started by: Chella15
3 Replies

6. Shell Programming and Scripting

sed replace range of characters in each line

Hi, I'm trying to replace a range of characters by their position in each line by spaces. I need to replace characters 95 to 145 by spaces in each line. i tried below but it doesn't work sed -r "s/^(.{94})(.{51})/\ /" inputfile.txt > outputfile.txt can someone please help me... (3 Replies)
Discussion started by: Kevin Tivoli
3 Replies

7. Shell Programming and Scripting

Replace characters infile with sed

I have several files in a directory that look like this: jacket-n r potential-n - outcome-n f reputation-n b I want to replace the characters in the second column with certain numbers. For instance, I want the letters 'f', 'r' and 'b' in the second column to replaced with 0 and I want the... (1 Reply)
Discussion started by: owwow14
1 Replies

8. Shell Programming and Scripting

sed replace nth characters with string

Hi, I hope you can help me out please? I need to replace from character 8-16 with AAAAAAAA and the rest should stay the same after character 16 gtwrhtrd11111111rjytwyejtyjejetjyetgeaEHT wrehrhw22222222hytekutkyukrylryilruilrGEQTH hrwjyety33333333gtrhwrjrgkreglqeriugn;RUGNEURGU ... (4 Replies)
Discussion started by: stinkefisch
4 Replies

9. Shell Programming and Scripting

sed replace characters using a wildcard

Hello, I have some data that looks like the following, > <SALTDATA> (OVS0199262) HCl > <IDNUMBER> (OVS0199262) OVS0199262 > <SUPPLIER> (OVS0199262) TimTec > <EMAIL> (OVS0199262) info@timtec.net > <WEBSITE> (OVS0199262) http://www.timtec.net I need to remove the data in... (3 Replies)
Discussion started by: LMHmedchem
3 Replies

10. Shell Programming and Scripting

sed command on AIX, replace specific characters

Hi, Im using sed on an AIX machine. I am trying to change the 137-139 characters if they are a ' 36'/'000' to a '036'. The positions that need to be changed are fixed. the source data that I have is$cat v.txt 4000422985400050462239065593606500000007422985707771046154054910075641MC0318AMWAY... (9 Replies)
Discussion started by: dsid
9 Replies

LEARN ABOUT DEBIAN

shtool-subst

SHTOOL-SUBST.TMP(1)					      GNU Portable Shell Tool					       SHTOOL-SUBST.TMP(1)

NAME

       shtool-subst - GNU shtool sed(1) substitution operations

SYNOPSIS

       shtool subst [-v|--verbose] [-t|--trace] [-n|--nop] [-w|--warning] [-q|--quiet] [-s|--stealth] [-i|--interactive] [-b|--backup ext]
       [-e|--exec cmd] [-f|--file cmd-file] [file] [file ...]

DESCRIPTION

       This command applies one or more sed(1) substitution operations to stdin or any number of files.

OPTIONS

       The following command line options are available.

       -v, --verbose
	   Display some processing information.

       -t, --trace
	   Enable the output of the essential shell commands which are executed.

       -n, --nop
	   No operation mode. Actual execution of the essential shell commands which would be executed is suppressed.

       -w, --warning
	   Show warning on substitution operation resulting in no content change on every file. The default is to show a warning on substitution
	   operations resulted in no content change on all files.

       -q, --quiet
	   Suppress warning on substitution operation resulting in no content change.

       -s, --stealth
	   Stealth operation. Preserve timestamp on file.

       -i, --interactive
	   Enter interactive mode where the user has to approve each operation.

       -b, --backup ext
	   Preserve backup of original file using file name extension ext.  Default is to overwrite the original file.

       -e, --exec cmd
	   Specify sed(1) command directly.

       -f, --file cmd-file
	   Read sed(1) command from file.

EXAMPLE

	#   shell script
	shtool subst -i -e 's;(c) ([0-9]*)-2000;(c) 1-2001;' *.[ch]

	#    RPM spec-file
	%install
	    shtool subst -v -n 
		-e 's;^(prefix=).*;1 $RPM_BUILD_ROOT%{_prefix};g' 
		-e 's;^(sysconfdir=).*;1 $RPM_BUILD_ROOT%{_prefix}/etc;g' 
		`find . -name Makefile -print`
	    make install

HISTORY

       The GNU shtool subst command was originally written by Ralf S.  Engelschall <rse@engelschall.com> in 2001 for GNU shtool.  It was prompted
       by the need to have a uniform and convenient patching frontend to sed(1) operations in the OpenPKG package specifications.

SEE ALSO

       shtool(1), sed(1).

18-Jul-2008							   shtool 2.0.8 					       SHTOOL-SUBST.TMP(1)
All times are GMT -4. The time now is 10:49 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy