can not execute a C script call "if"

araomai · 05-05-2007, 02:30 AM

Hi,

I am using Ubuntu 7.04.

I am starting to test C on Linux and something I do not really understand has happened. I created this simple script called "if.c":

#include <stdio.h>
int main(void) {
int test = 1;
if (test) {
printf ("*** Value of the test is %d.\n", test);
}
return 0;
}

So, the thing is...

1) If I compile it and name it "if":

$ gcc -g -o if if.c

If compiles OK, but when I execute it:

$ if
>

It doesn't run. I need to stop it with ctrl+c.

2) However, if I compile it with another name:

$ gcc -g -o maybe if.c

It does run!!!

$ maybe
*** Value of the test is 1.

Somebody knows what's going on? Is there any conflict with using "if" as the name?

Dark_Helmet · 05-05-2007, 02:38 AM

Quote:

Is there any conflict with using "if" as the name?

Yes. Specifically the bash builtin command "if" that you see used in scripts. More specifically, you will have a conflict with any other executable found in your PATH. That's why you should always preface your newly compiled executable with "./" as in:

Code:

./if

or

./maybe

Also, a C program is not commonly referred to as a "script"; it's more commonly referred to as a program. Calling it a "script" will likely lead to confusion.

elsheikhmh · 05-05-2007, 06:55 AM

Quote:

$ if
>

It doesn't run. I need to stop it with ctrl+c.

No, bash builtin's "if" runs and enters a kind of multiline mode after you hit enter, showing the prompt ">" waiting for you to enter the rest of the IF condition. It will terminate normally (not gracefully) by end-if keyword: "fi". try it:

Code:

$ if
> fi
sh: syntax error near unexpected token `fi'

-Mustafa

jim mcnamara · 05-06-2007, 06:44 AM

What everyone is telling you:
1. You created a compiled program that is named the same thing as a word in bash. Bash is your shell language.

2.

Code:

which if

will tell you the type of command or file you get by typing the word "if".

3. putting ./ in front of a filename means "use the current working directory" to find the file.