CODEWITHSUNDEEP
clinuxbash
Izzo
Izzo

Reputation: 4928

How do you execute a bash script with "system()" when there are spaces in the file path?

I created a simple bash script called "myscript.h" I gave it a .h extensions for reasons that I won't disclose here. This bash script lives in "/var/ftp/something with spaces".

From the terminal, I can type in "/var/ftp/something with spaces/myscript.h" and the script works perfectly.

However, from within my C program, I type in 

system("/var/ftp/something with spaces/myscript.h")

and it complains that "/var/ftp/something" is not found. I've changed my system call to the following with forward slashes:

system("/var/ftp/something\ with\ spaces/myscript.h")

However, it still complains that "/var/ftp/something" is not found. Assuming I can't change the directory names, how can I get around this?

Thanks!

Upvotes: 4

Views: 767

Answers (4)

Unwastable
Unwastable

Reputation: 679

This should work with gcc version 5.4.0

system("\'\'/var/ftp/something\\ with\\ spaces/myscript.h\'\'");

Upvotes: 0

Omar Alves
Omar Alves

Reputation: 763

Just put the filename inside single quotes

system("rm '/var/ftp/something with spaces/myscript.h'")

Upvotes: -1

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

To run a single script, you might avoid the system(3) library function (and use lower level system calls like fork(2), execve(2), waitpid(2)... which are used by the implementation of system(3)), or you could quote the script name when passing it to system(3).

For more details, read Advanced Linux Programming.

On Linux, system(3) is documented to fork a /bin/sh -c process. See sh(1p). And that POSIX shell has some quoting rules. You might use double-quotes and backslashes appropriately. So you would construct (and perhaps check) the string passed to system(3) (perhaps using asprintf(3) or snprintf(3) with care). Be aware that the C compiler also has (different) quoting conventions for string literals.

In general, you should avoid code injection (imagine a naughty user giving some a; rm -rf $HOME &; input as a "directory" name; you don't want to run system(3) on the weird
"/var/ftp/a; rm -rf $HOME &;/myscript.h" string)

In your particular case, I recommend using fork(2), execve(2) (perhaps thru some carefully choosen exec(3) function), waitpid(2)... appropriately. This has the slight advantage to avoid depending on and running /bin/sh so could be slightly faster (by a millisecond).

Understand more the role of an Unix shell; for example, read about the various shell expansions in bash (they are similar to those mandated by POSIX sh) and be aware of globbing. See glob(7)

Upvotes: 7

dbush
dbush

Reputation: 224387

Note that you're adding quotes when running from the shell. You need to do the same here. Add quotes to the path name you're sending to system:

system("\"/var/ftp/something with spaces/myscript.h\"")

Upvotes: 0

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