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Full Discussion: Insert a line in a text file
Top Forums Shell Programming and Scripting Insert a line in a text file Post 302220559 by bakunin on Friday 1st of August 2008 05:56:16 AM
Old 08-01-2008
Quote:
Originally Posted by 4scriptmoni
I like the sed one more, its just less complicated command.
Good guy! ;-))


Quote:
But both output to the screen I need it to write to that same file.
I tried

[...]

Is that the best way ?
Yes, more or less. sed principally does not overwrite the file it works on, so you have to save its results to a temporary file and copy/move the contents over the original afterwards. You can use "mv" instead of "cp", because you don't need a save copy of the results file, but thats a minor issue:

mv (instead of cp) new.txt servicegroup-24x7-comm.cfg

Quote:
Also I need to pass a variable to that command how do it do??
[...]
that prints $LINEX
The reason is, that sed commands might contain characters which have special meaning to the shell. To prevent the shell from being confused we usually surround all sed programs with single quotes, which do exactly this:

sed 'some_commands' file > file.new

Unfortunately this also prevents the special character "$" to be interpreted: An expression like "$variable" is in fact a command to the shell, saying: replace the string "$variable" with the content of the variable "variable". After preventing this interpretation this mechanism doesn't work any more, which is why you get the result "$LINEX" instead of the content of the variable LINEX. Therefore the solution is to find a way to exclude the variable expression from the single-quoted string:

sed '/alias 24x7-comunicacions/a\'"$LINEX" $FILECFG

I hope this helps.

bakunin
 

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SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.8.4 2005-05-03 SHELL-QUOTE(1p)
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