Option flags: -n, --ip_addr
Function: Return the IP address of the user by reading utmp. Return value in
ipv4 or ipv6 formats based upon the type of address stored. Disable DNS
lookup.
w010 ~ # who -n -l
root :0 Oct 8 13:52 [0.0.0.0]
root pts/0 Oct 8 13:53 [0.0.0.0] (:0)
root pts/1 Oct 8 17:42 [10.2.10.1] (s001.site2.cs.lan)
The IP address is unconditionally returned from the data in utmp. This
provides a security and functionality mechanism without needing to
reverse-resolve the DNS. Since the connection has already been made, the
resolver does not need to spend the time to return the IP address.
The -n option is syntactically correct with other uses of -n such as route.
The return values are enclosed in [] to differentiate from the cananonical
name that is enclosed in (). This is especially important when the resolver
is unable to do a lookup and the -l option returns the IP address.
The return value of [0.0.0.0] indicates that there is NO information in the
utmp for this connection as a positive indicator. This catches conditions
with some telnet/login combinations that do not properly update utmp.
The most common use for me is as follows:
w010 ~ # who am i -n
w010.site2.cs.lan!root pts/1 Oct 8 17:42 [10.2.10.1]
I use the IP address for distributed processing applications where the users
lan address is needed by the application software.
*** Diff ***
w203 src # diff -u who.c.orig who.c
--- who.c.orig 2006-10-08 13:35:34.000000000 -0400
+++ who.c 2006-10-08 13:57:35.000000000 -0400
@@ -16,6 +16,7 @@
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
/* Written by jla; revised by djm; revised again by mstone */
+/* Revised by Bill Crowell & Mike Isely to return IP address from utmp (-n)*/
/* Output format:
name [state] line time [activity] [pid] [comment] [exit]
@@ -155,6 +156,9 @@
static char const *time_format;
static int time_format_width;
+/* If true, display the IPv4 address of the user rather than the
+ hostname or resolved hostname of the user */
+static bool use_ipaddr;
/* for long options with no corresponding short option, use enum */
enum
{
@@ -178,6 +182,7 @@
{"time", no_argument, NULL, 't'},
{"users", no_argument, NULL, 'u'},
{"writable", no_argument, NULL, 'T'},
+ {"ipaddr", no_argument, NULL, 'n'},
{GETOPT_HELP_OPTION_DECL},
{GETOPT_VERSION_OPTION_DECL},
{NULL, 0, NULL, 0}
@@ -416,6 +421,59 @@
}
*hoststr = '\0';
}
+if (use_ipaddr)
+ {
+ char buf[100];
+ unsigned int len1,len2,spc;
+ buf[0] = '[';
+ len2 = 1;
+ if (utmp_ent->ut_addr_v6[1] ||
+ utmp_ent->ut_addr_v6[2] ||
+ utmp_ent->ut_addr_v6[3])
+ {
+ unsigned int idx;
+ unsigned short v;
+ /* Print IPV6 style */
+ for (idx = 0; idx < 8; idx++) {
+ v = (utmp_ent->ut_addr_v6[(7-idx) >> 1]) >>
+ (((7-idx) & 1) ? 0 : 16);
+ v = (v << 8) | (v >> 8);
+ if (idx)
+ {
+ buf[len2] = ':';
+ len2++;
+ }
+ if (v)
+ {
+ sprintf(buf+len2,"%x",v);
+ len2 += strlen(buf+len2);
+ }
+ }
+ }
+ else
+ {
+ /* Print IPV4 style */
+ sprintf(buf+len2,"%u.%u.%u.%u",
+ utmp_ent->ut_addr_v6[0] & 0xffu,
+ (utmp_ent->ut_addr_v6[0] >> 8) & 0xffu,
+ (utmp_ent->ut_addr_v6[0] >> 16) & 0xffu,
+ (utmp_ent->ut_addr_v6[0] >> 24) & 0xffu);
+ len2 += strlen(buf+len2);
+ }
+ buf[len2] = ']';
+ len2++;
+ len1 = hoststr ? strlen(hoststr) : 0;
+ spc = len1 ? 1 : 0;
+ if (hostlen < len1+len2+spc+1)
+ {
+ hostlen = len1+len2+spc+1;
+ hoststr = xrealloc(hoststr,len1+len2+spc+1);
+ }
+ if (spc) hoststr[len1] = ' ';
+ len1++;
+ memcpy(hoststr+len1,buf,len2);
+ hoststr[len1+len2] = 0;
+ }
#endif
print_line (sizeof UT_USER (utmp_ent), UT_USER (utmp_ent), mesg,
@@ -642,6 +700,7 @@
fputs (_("\
--lookup attempt to canonicalize hostnames via DNS\n\
-m only hostname and user associated with stdin\n\
+ -n, --ipaddr display IP address of hostname from utmp without DNS\n\
-p, --process print active processes spawned by init\n\
"), stdout);
fputs (_("\
@@ -682,7 +741,7 @@
atexit (close_stdout);
- while ((optc = getopt_long (argc, argv, "abdilmpqrstuwHT", longopts, NULL))
+ while ((optc = getopt_long (argc, argv, "abdilmnpqrstuwHT", longopts,
NULL))
!= -1)
{
switch (optc)
@@ -727,6 +786,11 @@
my_line_only = true;
break;
+ case 'n':
+ use_ipaddr = true;
+ do_lookup = false;
+ break;
+
case 'p':
need_initspawn = true;
assumptions = false;
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