@node _is_executable, io
@subheading Syntax

@example
#include <sys/stat.h>

int _is_executable(const char *path, int fhandle, const char *extension);
@end example

@subheading Description

This function determines if a file is executable under DOS/DJGPP
environment.  The file may be given either by its @var{path} or its file
handle @var{fhandle}.  If @var{extension} is non-NULL and non-empty, it
is used first to look up in a list of known extensions which determine
whether the file is executable.  (If the @code{_STAT_EXEC_EXT} bit of
the @code{_djstat_flags} global variable (@pxref{_djstat_flags}) is not
set, this step is skipped.)  If @var{extension} is unavailable or not
enough to determine the result, the first 2 bytes of the file are
checked to contain one of the known @cite{magic numbers} identifying the
file as executable.  If the file's 2 first bytes need to be read but the
read fails, 0 is returned and errno is set.  (The file is only searched
for magic number if the @code{_STAT_EXEC_MAGIC} bit of the
@code{_djstat_flags} variable is set.)

Note that if @code{_STAT_EXEC_MAGIC} is set, but @code{_STAT_EXEC_EXT}
is not, some files which shouldn't be flagged as executables (e.g., COFF
@file{*.o} object files) will have their execute bit set, because they
have the magic number signature at their beginning.  Therefore, only use
the above combination if you want to debug the list of extensions
provided in @file{is_exec.c} file from the library sources.

If the file passed by its handle was open as write-only, and the extension
alone isn't enough to determine whether the file is executable, then this
function returns 0, because it cannot look at the @cite{magic number}.

This function is used internally by @code{f?stat}; you are not supposed
to call it directly.

@subheading Return Value

1 for executable file, 0 otherwise (including in case of errors in
accessing the file).

@subheading Portability

@portability !ansi, !posix