Mail Archives: cygwin/2022/06/26/12:27:47

"Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\] via Cygwin" <cygwin AT cygwin DOT com> · Sun, 26 Jun 2022 16:26:35 +0000

There's another discrepancy for execlp() on Cygwin.  In the absence of the PATH environment, it should consider the current directory first, then look up somewhere else.
And it does so on Linux!  Not on Cygwin, though.  Please take a look below:

Linux:

$ ./hello
exec: No such file or directory
$ unset PATH
$ echo $PATH

$ ./hello
Hello

Cygwin:

$ ./hello
exec: No such file or directory
$ unset PATH

$ echo $PATH
$ ./hello
exec: No such file or directory

Anton Lavrentiev
Contractor NIH/NLM/NCBI

> -----Original Message-----
> From: Cygwin <cygwin-bounces+lavr=ncbi DOT nlm DOT nih DOT gov AT cygwin DOT com> On Behalf Of Lavrentiev,
> Anton (NIH/NLM/NCBI) [C] via Cygwin
> Sent: Sunday, June 26, 2022 11:10 AM
> To: 'cygwin AT cygwin DOT com' <cygwin AT cygwin DOT com>
> Subject: [EXTERNAL] Cygwin's execlp() does not work with an empty $PATH element
> 
> Hi all,
> 
> An empty PATH element (":xxx" or "xxx::xxx" or "xxx:") is to be considered as the current
> directory (from the very first days of Unix).
> 
> However, Cygwin does not seem to obey the rule.
> 
> Consider the following simple C program:
> 
> $ cat hello.c
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> 
> int main(int argc, const char* argv[])
> {
>     if (argc < 2) {
>         const char* prog = strrchr(argv[0], '/');
>         if (!prog++)
>            prog = argv[0];
>         execlp(prog, prog, "Hello", NULL);  // execute just by the program name
>         perror("exec");
>         return 1;
>     }
>     printf("%s\n", argv[1]);
>     return 0;
> }
> 
> Now compare the execution on Linux and Cygwin:
> 
> Linux:
> 
> $ gcc -Wall -o hello hello.c
> $ hello
> bash: hello: command not found
> $ ./hello
> exec: No such file or directory
> $ PATH=".:$PATH" ./hello
> Hello
> $ PATH=":$PATH" ./hello
> Hello
> $ PATH="${PATH}:" ./hello
> Hello
> 
> Cygwin:
> 
> $ gcc -Wall -o hello hello.c
> $ hello
> -bash: hello: command not found
> $ ./hello
> exec: No such file or directory
> $ PATH=".:$PATH" ./hello
> Hello
> $ PATH=":$PATH" ./hello
> exec: No such file or directory
> $ PATH="${PATH}:" ./hello
> exec: No such file or directory
> 
> As you can see, the execution failed when an empty PATH element was added on Cygwin
> (yet it was perfectly fine on Linux).
> 
> Anton Lavrentiev
> Contractor NIH/NLM/NCBI
> 
> 
> --
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To:	"'cygwin AT cygwin DOT com'" <cygwin AT cygwin DOT com>
Subject:	RE: Cygwin's execlp() does not work with an empty $PATH element
Thread-Topic:	Cygwin's execlp() does not work with an empty $PATH element
Thread-Index:	AdiJbrs+rXZuHXNaTrCqY66Eq3KrXAACh9EQ
Date:	Sun, 26 Jun 2022 16:26:35 +0000
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From:	"Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\] via Cygwin" <cygwin AT cygwin DOT com>
Reply-To:	"Lavrentiev, Anton \(NIH/NLM/NCBI\) \[C\]" <lavr AT ncbi DOT nlm DOT nih DOT gov>
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