Replacing patterns in a file

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# 1  
Old 08-25-2009
Question Replacing patterns in a file

Hi Everybody,

Can we replace the contents of a file without using a temporary file.

For ex:
I need to relpace the value "old" with "new", I can do it using the sed replace pattern, but I do not want to use a temporary file.

Also, from the questions posted in the past I could see a fantastic command to do this
printf '1,$ s/old/new/g\nw! samp.txt\nq!'| ex - samp.txt

But, with the same command I am not able to replace the value of a variable
For ex: var1='new'
printf '1,$ s/new/$var1/g\nw! samp.txt\nq!'| ex - samp.txt

The above command doesn't replace the value of the variable.
# 2  
Old 08-25-2009
You can use sed to replace stings without using a temp file using its -i (edit in place) flag.

Shell variables are not interpreted inside single quotes. You should use double quotes or terminate the single quote before $var and start it after $var.

$ printf '1,$ s/new/'$var1'/g\nw! samp.txt\nq!'| ex - samp.txt

# 3  
Old 08-25-2009
$ echo "this is old data">f1
$ cat f1
this is old data
$ perl -pi.bak -e 's/old/new/g' f1
$ ## backup
$ cat f1.bak
this is old data
$ ## new
$ cat f1
this is new data

# 4  
Old 08-25-2009
Hi agn,
Thanks for the input, it is working
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