comp.lang.c
c programs & shell conditionals

How is a unix shell script made to respond to the value returned
by a program compiled from c code?
The shell script below is my current effort, which doesn't work.
The c code shows what was used to generate a.out, seen in the shell script.
The value returned was varied from 0 to 1 for testing.


---- shell script
# if [ `/net/u/12/b/br/unet/a.out` > 0 ]
if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
then echo "result is positive"
else echo "result is not greater than zero"
fi

--- c program
int main(int argc, char **argv)
{
return 1; /* or return 0 or exit(0) or exit(1) */
}

In article <fnvdte$se2$1@reader2.panix.com>, Hul Tytus <ht@panix.com> wrote:
>comp.lang.c

> How is a unix shell script made to respond to the value returned
>by a program compiled from c code?
> The shell script below is my current effort, which doesn't work.
>The c code shows what was used to generate a.out, seen in the shell script.
>The value returned was varied from 0 to 1 for testing.

[re-ordered]

>--- c program
>int main(int argc, char **argv)
>{
> return 1; /* or return 0 or exit(0) or exit(1) */
>}

Nothing wrong here, except that EXIT_FAILURE is probably better than 1
(though there's a good chance that the value of EXIT_FAILURE is in fact
1 on your platform).


>---- shell script
># if [ `/net/u/12/b/br/unet/a.out` > 0 ]
>if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]

The people in comp.unix.shell will probably tell you that this line is
wrong.


dave

--
Dave Vandervies dj3vande at eskimo dot com

Their failure is not your excuse; time to find an unaverage pub.
--Richard Bos in the scary devil monastery

In article <fnvdte$se2$1@reader2.panix.com>, Hul Tytus <ht@panix.com> wrote:

>if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
>then echo "result is positive"
>else echo "result is not greater than zero"
>fi

You just want

if /net/u/12/b/br/unet/a.out
then ...

-- Richard
--
:wq

Hul Tytus wrote:
> comp.lang.c
> c programs & shell conditionals
>
> How is a unix shell script made to respond to the value returned
> by a program compiled from c code?
> The shell script below is my current effort, which doesn't work.
> The c code shows what was used to generate a.out, seen in the shell
> script. The value returned was varied from 0 to 1 for testing.
>
>
> ---- shell script
> # if [ `/net/u/12/b/br/unet/a.out` > 0 ]
> if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
> then echo "result is positive"
> else echo "result is not greater than zero"
> fi
>
> --- c program
> int main(int argc, char **argv)
> {
> return 1; /* or return 0 or exit(0) or exit(1) */
> }
OT here, comp.unix.programmer or comp.unix.shell might be more apropriate,
but the shell conditionals work diffeent from the C ones, in C non-zero is
true, in shell zero is true.

To make it topical: the only portable return values of main(), resp.
parameters of exit() are 0, EXIT_SUCCESS (which are equivalent) and
EXIT_FAILURE (which usually is 1, but doesn't have to be)

Bye, Jojo

Joachim Schmitz wrote:
> Hul Tytus wrote:
>> comp.lang.c
>> c programs & shell conditionals
>>
>> How is a unix shell script made to respond to the value returned
>> by a program compiled from c code?
>> The shell script below is my current effort, which doesn't work.
>> The c code shows what was used to generate a.out, seen in the shell
>> script. The value returned was varied from 0 to 1 for testing.
>>
>>
>> ---- shell script
>> # if [ `/net/u/12/b/br/unet/a.out` > 0 ]
>> if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
>> then echo "result is positive"
>> else echo "result is not greater than zero"
>> fi
>>
>> --- c program
>> int main(int argc, char **argv)
>> {
>> return 1; /* or return 0 or exit(0) or exit(1) */
>> }
> OT here, comp.unix.programmer or comp.unix.shell might be more
> apropriate, but the shell conditionals work diffeent from the C ones,
> in C non-zero is true, in shell zero is true.
Uhh...perils of answering OT questions...
the `cmd` syntax would require your progarm to print a value. And in that
case redirecting the output to /dev/null doesn't make sense and also you'd
need something to test thie against

> To make it topical: the only portable return values of main(), resp.
> parameters of exit() are 0, EXIT_SUCCESS (which are equivalent) and
> EXIT_FAILURE (which usually is 1, but doesn't have to be)

Bye, Jojo

Thanks Jojo - I'll give that a try. Do you know what .h file contains
the definitions for EXIT_xxx?

Hul

Joachim Schmitz <nospam.jojo@schmitz-digital.de> wrote:
> Hul Tytus wrote:
> > comp.lang.c
> > c programs & shell conditionals
> >
> > How is a unix shell script made to respond to the value returned
> > by a program compiled from c code?
> > The shell script below is my current effort, which doesn't work.
> > The c code shows what was used to generate a.out, seen in the shell
> > script. The value returned was varied from 0 to 1 for testing.
> >
> >
> > ---- shell script
> > # if [ `/net/u/12/b/br/unet/a.out` > 0 ]
> > if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
> > then echo "result is positive"
> > else echo "result is not greater than zero"
> > fi
> >
> > --- c program
> > int main(int argc, char **argv)
> > {
> > return 1; /* or return 0 or exit(0) or exit(1) */
> > }
> OT here, comp.unix.programmer or comp.unix.shell might be more apropriate,
> but the shell conditionals work diffeent from the C ones, in C non-zero is
> true, in shell zero is true.

> To make it topical: the only portable return values of main(), resp.
> parameters of exit() are 0, EXIT_SUCCESS (which are equivalent) and
> EXIT_FAILURE (which usually is 1, but doesn't have to be)

> Bye, Jojo

Thanks - I had a definite feeling of being in the wrong ball park.

Hul

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:
> In article <fnvdte$se2$1@reader2.panix.com>, Hul Tytus <ht@panix.com> wrote:

> >if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]
> >then echo "result is positive"
> >else echo "result is not greater than zero"
> >fi

> You just want

> if /net/u/12/b/br/unet/a.out
> then ...

> -- Richard
> --
> :wq

Thanks, Hul

dj3vande@csclub.uwaterloo.ca.invalid wrote:
> In article <fnvdte$se2$1@reader2.panix.com>, Hul Tytus <ht@panix.com> wrote:
> >comp.lang.c

> > How is a unix shell script made to respond to the value returned
> >by a program compiled from c code?
> > The shell script below is my current effort, which doesn't work.
> >The c code shows what was used to generate a.out, seen in the shell script.
> >The value returned was varied from 0 to 1 for testing.

> [re-ordered]

> >--- c program
> >int main(int argc, char **argv)
> >{
> > return 1; /* or return 0 or exit(0) or exit(1) */
> >}

> Nothing wrong here, except that EXIT_FAILURE is probably better than 1
> (though there's a good chance that the value of EXIT_FAILURE is in fact
> 1 on your platform).


> >---- shell script
> ># if [ `/net/u/12/b/br/unet/a.out` > 0 ]
> >if [ `/net/u/12/b/br/unet/a.out` > /dev/null ]

> The people in comp.unix.shell will probably tell you that this line is
> wrong.


> dave

> --
> Dave Vandervies dj3vande at eskimo dot com

> Their failure is not your excuse; time to find an unaverage pub.
> --Richard Bos in the scary devil monastery

dbr@kbrx.com wrote:
> Thanks Jojo - I'll give that a try. Do you know what .h file contains
> the definitions for EXIT_xxx?
>
a quick grep would show...

but it should be stdlib.h

Bye, Jojo

Hul Tytus wrote:
> comp.lang.c
> c programs & shell conditionals
>
> How is a unix shell script made to respond to the value returned
> by a program compiled from c code?


<OT>

I recommend, though it's old and possibly out of print, getting hold of
"The Unix Programming Environment" by Kernighan and Pike.

A very short book but, as is usual when Brian Kernighan's involved, a
very clear and useful text. This sort of issue is covered.

</OT>

"Joachim Schmitz" <nospam.jojo@schmitz-digital.de> writes:
> dbr@kbrx.com wrote:
>> Thanks Jojo - I'll give that a try. Do you know what .h file contains
>> the definitions for EXIT_xxx?
>>
> a quick grep would show...
>
> but it should be stdlib.h

A quick grep could easily show something irrelevant like, say, a C++
"cstdlib" header, or some other system header from which <stdlib.h>
gets the EXIT_SUCCESS and EXIT_FAILURE definitions, and which might
not exist on another platform. <stdlib.h> is the right header to
include in your program. (The documentation for the exit() function
or a good C reference should tell you this.)

--
Keith Thompson (The_Other_Keith) <kst-u@mib.org>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"