Sponsored Content
Full Discussion: Sed command in shell script
Top Forums Shell Programming and Scripting Sed command in shell script Post 302211953 by Todd88 on Saturday 5th of July 2008 11:26:16 AM
Old 07-05-2008
Sed command in shell script

I have a current code working(named subst1) having a user be able to type this line to substitute words using the sed command:

Code:
subst1 old-pattern new-pattern filename

Here is my shell script:

Code:
#!/bin/bash
# subst1

ARGS=3
E_BADARGS=65

if [ $# -ne "$ARGS" ]
then
  echo "Usage: `basename $0` old-pattern new-pattern filename"
  exit $E_BADARGS
fi

old_pattern=$1
new_pattern=$2

if [ -f "$3" ]
then
    file_name=$3
else
    echo "File \"$3\" does not exist."
    exit $E_BADARGS
fi

mv $file_name $file_name.bak
sed -e "s/$old_pattern/$new_pattern/g" $file_name.bak > $file_name

exit 0

The problem with this script is that it changes the date and creates a bak file. I need to alter this script so that when a user inputs the command line, the script checks if the given old-pattern is in the file and if it is, go ahead and do the substitution. If the old-pattern is not found, the script should do nothing. Any help would be appreciated!
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

problem with sed command in shell script.

Guys, I've a problem in the "sed" command used in my shellscripts This is the problamatic line in my shell script: sed -e 's/${line1}/${line1_m}/g' prod_hier_1234.txt > test.txt It doesn't do the job of replacing the string stored in variable 'line1' to 'line1_m'. However If I replace the... (10 Replies)
Discussion started by: bhagat.singh-j
10 Replies

2. Shell Programming and Scripting

Quick Question on sed command in shell script

Hello, I have the following line in one of my shell scripts. It works fine when the search string($SERACH_STR) exists in the logfile($ALERTLOG) but if the search string does not exist this line errors out at run time. Is there a way to make this line return 0 if it is not able to find the... (4 Replies)
Discussion started by: luft
4 Replies

3. Shell Programming and Scripting

Need help using sed command in shell script?

Hello, i want to take the input from user and according to that variable's value search in file emp.lst. Here is what i came up with echo -e "Enter string to be searched :\c" read str sed -n '/\$str/p' emp.lst this is not working! any idea why?Thanks in advance! :) (4 Replies)
Discussion started by: salman4u
4 Replies

4. Shell Programming and Scripting

"sed" command is not working in shell script

Hi All, I am not much strong in shell scripting... I am using sed command in my script to find and replace a string....... This is how script looks : ############# #!/usr/bin/ksh CONFIG_FILE=iom_test.txt FIND=`echo "NIS_FTP_SERVER1=123.456.iom.com"` REPLACE=`echo... (2 Replies)
Discussion started by: askumarece
2 Replies

5. Shell Programming and Scripting

shell script/sed command help

First off I have read the man pages for sed and am still having trouble working on a script to remove portions of a log: My goal is to take a log file to be emailed, read the file and strip the portions away AFTER the line MIME-Version:1.0 and strip away until it to the line starting with... (4 Replies)
Discussion started by: murphybr
4 Replies

6. Shell Programming and Scripting

Using SED command in a shell script: Unterminated address regex

Hi All, I am trying to use a sed command in a shell script in order to delete some lines in a file and I got the following error message. I don't understand why it is not working 'cause I have tried with simple quotes, then with double-quotes, and it is not working. sed: -e expression #1,... (7 Replies)
Discussion started by: Alpha3363
7 Replies

7. Shell Programming and Scripting

sed command using variables in shell script

hi guys, The following command doesn't seem to work in my shell script: tag=$(sed -n '/${line}/ s/.*\.*/\1/p' myfile.txt) When i replace the ${line} with an actual value, it works fine. So, how do i use the ${line} in this sed command? Thanks in advance, Zaff (2 Replies)
Discussion started by: zaff
2 Replies

8. Shell Programming and Scripting

Unable to pass shell script variable to awk command in same shell script

I have a shell script (.sh) and I want to pass a parameter value to the awk command but I am getting exception, please assist. diff=$1$2.diff id=$2 new=new_$diff echo "My id is $1" echo "I want to sync for user account $id" ##awk command I am using is as below cat $diff | awk... (2 Replies)
Discussion started by: Ashunayak
2 Replies

9. Shell Programming and Scripting

sed command not accepting variable in shell script

I am using a shell script in fedora linux. While calling to the shell I am also passing an argument (var1=0.77) like shown below sh gossip.sh var1=0.77 in the shell following command is written (which doesn't work) sed - i -e 's@prob=@prob="$var1";//@g' file.txt Actually i want the... (7 Replies)
Discussion started by: Fakhar Hassan
7 Replies

10. Shell Programming and Scripting

sed working on command line but file unchanged when execute with Shell script

I have a simple task to replace unix line feed end of line characters with carriage returns. When I run the following “change file in place” sed instruction from the command line all the Line feeds are successfully replaced with Carriage returns. sed -i 's/$/\r/' lf_file.txt But that same... (1 Reply)
Discussion started by: hawkman2k
1 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 01:37 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy