Why are my backslashes disappearing in my Perl one-liner?

Question

I tried a search and replace across all files in a directory as follows:

/usr/bin/perl -p -i -e "s/Else/Else  FILE_WRITE(\"C:\\TestDir\\mes.txt","Message received");/g"            *.scr

That is replace all occurence of Else with "Else FILE_WRITE(\"C:\TestDir\mes_.txt","Message received");"

But the replacement is seen to be as follows:

Else  FILE_WRITE("C:TestDir^@mes.txt);

What am I missing?

Answer 1

This is actually a shell question, not a Perl question.

You need to escape the slashes in the filename, otherwise the shell will interpret them as escape sequences.

What you have right now:

$ echo "s/Else/Else FILE_WRITE(\"C:\TestDir\mes.txt","Message received");/g"
bash: syntax error near unexpected token `)'

What you want:

$ echo "s/Else/Else FILE_WRITE(\"C:\\TestDir\\mes.txt\",\"Message received\");/g"
s/Else/Else FILE_WRITE("C:\TestDir\mes.txt","Message received");/g

In the future, try to use single quotes instead of double quotes. Then you can write without escaping:

$ echo 's/Else/Else FILE_WRITE("C:\TestDir\mes.txt","Message received");/g'
s/Else/Else FILE_WRITE("C:\TestDir\mes.txt","Message received");/g

Perl's flexible q and qq operators are also helpful:

$ perl -e 'print q{A double quote looks like this -> "}'
A double quote looks like this -> "