Technorama

Ever seen the message "No such file or directory" when you open a file? Why is it considered possibly a directory...?

Example:

$ cat missingfile
cat: missingfile: No such file or directory
$ mkdir testdir
$ cat testdir
cat: testdir: Is a directory

Logically a directory is not the same as a file. UNIX got this wrong. So all our tools will output "No such file or directory", when the tool was trying to read a file. Or a tool that processes directories will output the same.

What is the solution? Soem ideas

A) Change POSIX. Introduce ENOFILE or ENODIR. Call opendir() and you'll get ENODIR, call open() and you'll get ENOFILE.
Retain ENOENT for backwards compatibility.

B) Provide some system level wrapped strerror()?

/* Set file to -1 if ignored, 0 if a file, or 1 if a directory */
char * wrap_strerror(int errnum, int file)
{
switch(file)
{
case 0:
{
return "No such file";
}
case 1:
{
return "No such directory";
}
case -1:
default:
{
return strerror(errnum);
}
}
}

A complete implementation of this would localise the strings.

While we are at this, can we add errnotostr(int errnum) which returns codes like "EBADF" to make debugging logs clearer.

I favour (A), could be rolled out as a glibc update.