Re: [PATCH v3 1/6] t9001: non order-sensitive file comparison

Junio C Hamano [off-list ref] writes:

Tom Russello [off-list ref] writes:

quoted

+# Check if two files have the same content, non-order sensitive
+test_cmp_noorder () {
+	sort $1 >$1;

Here is what I think happens:

    0) the shell parses this command line;
    1) the shell notices that the output has to go to $1;
    2) the shell does open(2) of $1,
    3) the shell spawns "sort" with a single argument, with its
       output connected to the file descriptor obtained in 2).

Because "$1" becomes an empty file at 2), "sort" reads nothing and
writes nothing.

Tom: in case you're not convinced, try this:

$ (echo b; echo a) >f
$ sort f
a
b
$ sort f >f
$ cat f
$

Also, useless ';' and missing double-quotes around "$1" to avoid bad
surprises ifever test_cmp_noorder is called on file names with special
characters.

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

On 06/09/16 07:51, Matthieu Moy wrote:

Junio C Hamano [off-list ref] writes:

quoted

Tom Russello [off-list ref] writes:

quoted

+# Check if two files have the same content, non-order sensitive
+test_cmp_noorder () {
+	sort $1 >$1;

Here is what I think happens:

    0) the shell parses this command line;
    1) the shell notices that the output has to go to $1;
    2) the shell does open(2) of $1,
    3) the shell spawns "sort" with a single argument, with its
       output connected to the file descriptor obtained in 2).

Because "$1" becomes an empty file at 2), "sort" reads nothing and
writes nothing.

Tom: in case you're not convinced, try this:

$ (echo b; echo a) >f
$ sort f
a
b
$ sort f >f
$ cat f
$

Also, useless ';' and missing double-quotes around "$1" to avoid bad
surprises ifever test_cmp_noorder is called on file names with special
characters.

I was totally convinced by Junio's explanation, it is partially fixed in
v4 and will be entirely fixed in v5.

Thanks.