bash does not recognize executable Perl script

Question

I have a very mysterious problem with bash and/or perl. I'll try to describe the behaviour.

Running a perl script via

./perlscript.pl

gives me a permission denied message.

(I am the owner of the file and the path to it -from my home dir and the file contains #!/usr/bin/perl and is executable -rwxr-xr-x )

Running the script like this:

perl perlscript.pl

is ok...

Can anyone please help me fix my bash? Thank you

$ which perl
/usr/bin/perl

$ head -1 file.pl | od -c
0000000 # ! / u s r / b i n / p e r l \n
0000020

Did you mean to say !#/usr/bin/perl or was that a typo? The correct directive is #!/usr/bin/perl or better #!/usr/bin/env perl. — Hunter McMillen
– Hunter McMillen, Commented Jan 21, 2015 at 16:45
@Karlo, egrep won't find \r\n because grep is a line oriented tool (grep will not ever find \n). Try: head -1 file.pl | od -c — glenn jackman
– glenn jackman, Commented Jan 21, 2015 at 17:03
strace ./perlscript.pl vs strace perl ./perlscript.pl ... to find differences — philippe lhardy
– philippe lhardy, Commented Jan 21, 2015 at 19:07

cjm · Accepted Answer · 2015-01-21 22:38:17Z

6

Is the filesystem where perlscript.pl is located mounted with the noexec flag?

Assuming you're on Linux, cat /proc/mounts and look for noexec on the line with the appropriate filesystem.

The noexec flag prevents anyone from calling exec on a file located on that filesystem (which is what bash does when you do ./perlscript.pl). But perl perlscript.pl calls exec on /usr/bin/perl, which then opens perlscript.pl for reading.

Files on a noexec-mounted filesystem can still have execute permission, they just can't make use of it.

edited Jan 21, 2015 at 22:38

answered Jan 21, 2015 at 19:46

cjm

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2 Comments

philippe lhardy Over a year ago

i was thinking to the very same, i tested it with a localy mounted filesystem and bingo : if as root i mount -o loop,noexec empty mounted => as my user : cd mounted ./perlscript.pl fails, . AND file is still visible with +x rights... now waiting for the confirmation from @Karlo...

Karol Pal Over a year ago

Yes, thats is the problem. I moved my home directory to a mounted storage space and the 'cat /proc/mounts' has noexec next to it... thank you!!

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