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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!
 

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LEARN ABOUT LINUX

fc-pattern

FC-PATTERN(1)                                                                                                                        FC-PATTERN(1)

NAME

       fc-pattern - parse and show pattern

SYNOPSIS

       fc-pattern [ -cdVh ] [ --config ] [ --default ] [ -f format | --format format ] [ --version ] [ --help ]
           [ pattern  [ element ... ]  ]

DESCRIPTION

       fc-pattern  parses  pattern (empty pattern by default) and shows the parsed result.  If --config is given, config substitution is performed
       on the pattern before being displayed.  If --default is given, default substitution is performed on the pattern before being displayed.

       If any elements are specified, only those are printed.

OPTIONS

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

       -c --config
              Perform config substitution on pattern.

       -d --default
              Perform default substitution on pattern.

       -f --format format
              Format output according to the format specifier format.

       -V --version
              Show version of the program and exit.

       -h --help
              Show summary of options.

       pattern
              Parses and displays pattern (uses empty pattern by default).

       element
              If set, the element property is displayed for parsed pattern.

SEE ALSO

       FcNameParse(3)  FcConfigSubstitute(3)  FcDefaultSubstitute(3)  FcPatternPrint(3)  FcPatternFormat(3)  fc-cat(1)  fc-cache(1) fc-list(1) fc-
       match(1) fc-query(1) fc-scan(1)

       The fontconfig user's guide, in HTML format: /usr/share/doc/fontconfig/fontconfig-user.html.

AUTHOR

       This manual page was updated by Behdad Esfahbod <behdad@behdad.org>.

                                                                   16 April 2012                                                     FC-PATTERN(1)
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