src/user/perms.nsc

include "syscalls.nsh";
include "lib.nsh";
include "string.nsh";
include "stdio.nsh";
 
/* perms file -- prints the r/w/x bits chmod actually set (r=1 w=2
 * x=4, kaboom's own single-digit bitmask, not real unix's owner/
 * group/other octal -- see chmod.nsc's own note), as "<name>: <digit>
 * <rwx>" (e.g. "/file: 3 rw-") -- both the digit AND the letters,
 * since chmod itself now takes either form (see chmod.nsc), and this
 * is the one place that shows what a name is actually set to.
 * chmod (kfs_chmod) could only ever WRITE a perm bit before this, and
 * kfs_check_perm only ever checked one internally -- nothing exposed
 * reading one back out to userspace at all, so there was no way to
 * actually see what a previous chmod left a file at short of it
 * failing or succeeding. sys_getperm (idt.nsc syscall 24) /
 * kfs_getperm (kfs.nsc) are that read-back path now.
 */
global i32
main(i32 argc, ptr argv)
{
	ptr name;
	u64 name_len;
	i64 perm;
	i8 out[3];
	i8 digit[1];
 
	if(argc < 2)
	{
		fputs(2, "usage: perms file\n");
		return 1;
	}
 
	name = argv_get(argv, 1);
	name_len = strlen(name);
	perm = (i64)sys_getperm(name, name_len);
	if(perm < (i64)0)
	{
		print_err(2, "perms", "not found");
		return 1;
	}
 
	if((perm & (i64)1) != (i64)0)
	{
		out[0] = (i8)114; /* 'r' */
	}
	else
	{
		out[0] = (i8)45; /* '-' */
	}
	if((perm & (i64)2) != (i64)0)
	{
		out[1] = (i8)119; /* 'w' */
	}
	else
	{
		out[1] = (i8)45; /* '-' */
	}
	if((perm & (i64)4) != (i64)0)
	{
		out[2] = (i8)120; /* 'x' */
	}
	else
	{
		out[2] = (i8)45; /* '-' */
	}
 
	digit[0] = (i8)(perm + (i64)48); /* '0'-'7' */
 
	/* fputs/sys_write only, deliberately -- putchar buffers and only
	 * flushes on a newline or a full buffer (stdio.nsc), while fputs
	 * and sys_write are both immediate; mixing them mid-line reorders
	 * output (an immediate write can leapfrog a still-buffered
	 * putchar byte sitting ahead of it). every piece of this line
	 * goes out the same, immediate way instead. */
	sys_write(1, name, name_len); /* argv string, not a literal -- stays sys_write */
	fputs(1, ": ");
	sys_write(1, &digit[0], (u64)1);
	fputs(1, " ");
	sys_write(1, &out[0], (u64)3);
	fputs(1, "\n");
	return 0;
}