Unable to match a backslash inside system command

[nithinpes]

I will boil down my exact requirement to this: I should print out lines that do not contain semi-colon, backslash and closing parentheses. The following one -liner works fine.

perl -ne "unless(/[\\);]/) {print}" in.txt > out.txt
 

Consider the following sample data:

Msg_create(….); \
PSLogI18N\
Free( ….) 
eweqwdeqwe;
erwerwfrrfreer)
rwerttrwerterter\
rtwert)
et
er
te
t
wwwwwwwwwwwwwww\\
erwerrwerr  ;
 

But if I use the same one-liner inside a system() command in a script, backslash(\) will not be matched by the regex. Lines containing backslash will be printed out to out.txt.

system("perl -ne \"unless(/[\\);]/) {print}\" in.txt > out.txt");
 

This is quite puzzling! Even I tried putting backslash within \Q and \E and using reverse quotes and exec() instead of system command. Got the same results :(

[KevinADC]

try with 4 backslashes:

[\\\\);]

My thinking is that you have to escape two of them for the shell first, then you end up with [\\);] for perl to work with.

[nithinpes]

Yes, you are right. It worked :)

Thanks,
Nithin

[KevinADC]

ahhhh..... lucky guess then. You're welcome. Kind of odd though to use a perl script to run a perl one-liner from the shell. Why not just write it all in the perl script?

[nithinpes]

In my script I would be parsing hundreds of files. The input and output filenames would be variables. I prefer writing it all in the perl script, but used this approach to reduce few lines (open & close statements). Came across this issue and wanted to know why..