How to use *.* parameter in the exec family functions?

[andylcx]

Hi all:
I have one question about the system call under Unix system. I would
like to copy all the files in the current directory to a destination
directory using the following code, but it does not work. Any idea?
Thanks in advance!
if (fork() == 0)
{
execl("/usr/bin/cp", "cp", "*.*", "destinatio n", (char*)0);
}

[Joona I Palaste]

an*****@hotmail .com scribbled the following:

Hi all:
I have one question about the system call under Unix system. I would
like to copy all the files in the current directory to a destination
directory using the following code, but it does not work. Any idea?
Thanks in advance!
if (fork() == 0)
{
execl("/usr/bin/cp", "cp", "*.*", "destinatio n", (char*)0);
}

comp.lang.c reply: Ask in comp.unix.progr ammer.
Off-topic reply: *.* is a feature of the shell, not the Unix system
itself. The way you're doing it, cp attempts to copy a file that is
actually named "*.*". You need to execl() a shell and give "cp *.*
destination" as its parameter.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"Life without ostriches is like coffee with milk."
- Mika P. Nieminen

[Dag-Erling Smørgrav]

an*****@hotmail .com writes:

I have one question about the system call under Unix system. I would
like to copy all the files in the current directory to a destination
directory using the following code, but it does not work. Any idea?
This newsgroup is for questions about C, not about Unix, but I will
answer nonetheless.
if (fork() == 0)
{
execl("/usr/bin/cp", "cp", "*.*", "destinatio n", (char*)0);
}

First of all, Unix programs don't expand glob patterns in command-line
arguments. They expect their parent (normally the shell) to do it for
them. When you run the above code, cp tries to copy a file named,
literally, "*.*" (without the quotes).

Second, the glob pattern "*.*" will only match files whose name
contains a period. In DOS, there is always a period, even in file
names without extensions ("C:\README" and "C:\README. " are the same
file), so "*.*" will match all files, but it won't in Unix.

Third, execl() may fail, and bad things will probably happen if you
don't exit immediately (preferrably by calling _exit(), not exit())
when it does.

DES
--
Dag-Erling Smørgrav - de*@des.no

[SM Ryan]

an*****@hotmail .com wrote:
# Hi all:
# I have one question about the system call under Unix system. I would
# like to copy all the files in the current directory to a destination
# directory using the following code, but it does not work. Any idea?

Unless you need to do something fancy like redirect stdin or stderr,
you can do with the ANSI C function system(). It will take care of
expanding *.* for you which the exec* functions will not.

Just to remember to 'quote' file names in the system() call that you would
need to quote if typing it in at the command prompt.

# if (fork() == 0)
# {
# execl("/usr/bin/cp", "cp", "*.*", "destinatio n", (char*)0);
# }

int exitcode = system("/usr/bin/cp *.* destination");
if (exitcode!=0) {awk! an error occurred!}

or perhaps

char *destination = ....;
....
static char F[] = "/usr/bin/cp *.* '%s'";
char *f = malloc((sizeof F)+strlen(desti nation));
sprintf(f,F,des tination);
int exitcode = system(f);
free(f);
if (exitcode!=0) {awk! an error occurred!}
--
SM Ryan http://www.rawbw.com/~wyrmwif/
This is one wacky game show.

[Keith Thompson]

SM Ryan <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> writes:

an*****@hotmail .com wrote:

Hi all:
I have one question about the system call under Unix system. I would
like to copy all the files in the current directory to a destination
directory using the following code, but it does not work. Any idea?

Unless you need to do something fancy like redirect stdin or stderr,
you can do with the ANSI C function system(). It will take care of
expanding *.* for you which the exec* functions will not.

Just to remember to 'quote' file names in the system() call that you would
need to quote if typing it in at the command prompt.

['#' remapped to '>' yet again]

More precisely, system-specific entity that processes the command
string will presumably take care of expanding wildcards in some
system-specific manner.

<OT>
On Unix-like systems, the system() function invokes the shell,
/bin/sh, with the given command string as an argument. If you don't
go through the shell (e.g., if you use one of the system-specific
exec*() function), your wildcards aren't going to be expanded, and the
literal string is going to be passed directly to the /usr/bin/cp
command, which won't know what to do with it unless there happens to
be a file called "*.*".

And of course, given the usual Unix semantics, this will copy only
files whose names whose names contain a '.' character *and* don't
start with '.' -- which is great if that happens to be what you want.

For more information, try comp.unix.progr ammer.
</OT>

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.