From mboxrd@z Thu Jan  1 00:00:00 1970
From: arisawa <arisawa@ar.aichi-u.ac.jp>
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Message-Id: <18ADB858-4CC7-4A12-8408-57552185113E@ar.aichi-u.ac.jp>
Date: Sat,  9 Mar 2013 22:38:21 +0900
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: [9fans] DEL code in file name
Topicbox-Message-UUID: 25776392-ead8-11e9-9d60-3106f5b1d025

Hello,

DEL code is allowed in file name?

I find the following code in cwfs/sub.c.

/*
 * what are legal characters in a name?
 * only disallow control characters.
 * a) utf avoids control characters.
 * b) '/' may not be the separator
 */
int
checkname(char *n)
{
	int i, c;

	if(n == 0 || *n == 0)
		return Ename;
	if(*n == '.' && (n[1] == 0 || (n[1] == '.' && n[2] == 0)))
		return Edot;
	for(i=1; i<NAMELEN; i++) {
		c = n[i] & 0xff;
		if(c == 0)
			return 0;
		if(c < 040)
			return Ename;
	}
	return Etoolong;
}

I have believed DEL code is one of control code
and should not be allowed in file name.
so I experimented.

maia% cat a.c
#include <u.h>
#include <libc.h>

void
usage(void)
{
	fprint(2,"usage: 8.out [-n] ....\n");
	exits("usage");
}


void
main(int argc, char *argv[])
{	int fd;
	ARGBEGIN{
	default: usage();
	}ARGEND

	//fd = create("a\xffb",OWRITE,0664);// accepted
	//fd = create("",OWRITE,0664);// rejected
	fd = create("\xff",OWRITE,0664);// accepted
	//fd = create("\x07",OWRITE,0664);// rejected
	if(fd < 0)
		sysfatal("not open %r");
	write(fd,"abc",3);
	close(fd);
}

# cwfs64x
term% ls -l
--rw-rw-r-- M 20 arisawa arisawa     3 Mar  9 21:39 ''
--rwxrwxr-x M 20 arisawa arisawa 36671 Mar  9 21:39 8.out
--rw-rw-r-- M 20 arisawa arisawa     3 Mar  2 22:13 a
--rw-rw-r-- M 20 arisawa arisawa  1858 Mar  9 21:39 a.8
--rw-r--r-- M 20 arisawa arisawa   602 Mar  9 21:39 a.c
--rw-rw-r-- M 20 arisawa arisawa  2526 Mar  6 20:59 dirty.txt
--rw-r--r-- M 20 arisawa arisawa   303 Mar  2 22:10 mkfile

# fossil
ar% ls -l
--rwxrwxr-x M 769572 arisawa arisawa 37602 Mar  9 22:18 8.out
--rw-rw-r-- M 769572 arisawa arisawa  1882 Mar  9 22:18 a.8
--rw-r--r-- M 769572 arisawa arisawa  1509 Mar  9 22:18 a.c
--rw-rw-r-- M 769572 arisawa arisawa     3 Mar  9 22:18 a
--rw-rw-r-- M 769572 arisawa arisawa  2526 Mar  6 20:59 dirty.txt
--rw-r--r-- M 769572 arisawa arisawa   303 Mar  2 22:10 mkfile
--rw-rw-r-- M 769572 arisawa arisawa     3 Mar  9 22:16

the result on cwfs64 and fossil are same. DEL code is accepted in file name.
"\xff" appears as zero length name,
"a\xffb" appears as like "a"
both files cannot be removed by rm command.