RE: why is grep behaving this way ?
Yes, There are lots of alternatives like : who | grep `id -un` who | grep bhasker or even i tried to do this !!! who a grep `logname` a that WORKS ONLY this command who | grep `logname` does not work ! WHY ? Here's another workaround: NAME=`logname`;who|grep $NAME -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: why is grep behaving this way ?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 03/05/07 12:47, Kevin Ross wrote: Yes, There are lots of alternatives like : who | grep `id -un` who | grep bhasker or even i tried to do this !!! who a grep `logname` a that WORKS ONLY this command who | grep `logname` does not work ! WHY ? Here's another workaround: NAME=`logname`;who|grep $NAME Defensive programming! NAME=`logname` who|grep $NAME -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFF7GyVS9HxQb37XmcRAjCpAJ9HabvHbgRYDqmSo0wxUwMoN935pwCfWiGc uSpLLw2HQrcz9XIxXRRrfsA= =sSPG -END PGP SIGNATURE- -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
why is grep behaving this way ?
I have logname command give me this output [EMAIL PROTECTED] ~]$ logname bhaskerv and say i execute this command [EMAIL PROTECTED] ~]$ echo `logname` bhaskerv till this it is all fine BUT [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. is there anything i am doing wrong ?
Re: why is grep behaving this way ?
On Fri, Mar 02, 2007 at 03:07:37PM +0530, Bhasker C V wrote: [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. Weird. Consiedering that this works: who | grep `whoami` Where's the catch? -- Salvatore Iovene http://www.iovene.com signature.asc Description: Digital signature
Re: why is grep behaving this way ?
Salvatore Iovene wrote: On Fri, Mar 02, 2007 at 03:07:37PM +0530, Bhasker C V wrote: [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. Weird. Consiedering that this works: who | grep `whoami` Where's the catch? I'm running SuSE, and can reproduce the problem here. Seems logname does something weird when stdin is not your tty. Check this out: [EMAIL PROTECTED]:0$ logname/dev/null logname: no login name My manual-page has nothing to say. Try looking at the source if you must. -- Håkon Alstadheim spamtrap: [EMAIL PROTECTED] -- 1 hit you are out -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: why is grep behaving this way ?
On Fri, Mar 02, 2007 at 03:07:37PM +0530, Bhasker C V wrote: [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. On 02.03.07 11:27, H?kon Alstadheim wrote: I'm running SuSE, and can reproduce the problem here. Seems logname does something weird when stdin is not your tty. Check this out: [EMAIL PROTECTED]:0$ logname/dev/null logname: no login name My manual-page has nothing to say. Try looking at the source if you must. I'd say that logname detects logged user by checking terminal of stdin file handle... However, that's logname feature, use whoami or different utility -- Matus UHLAR - fantomas, [EMAIL PROTECTED] ; http://www.fantomas.sk/ Warning: I wish NOT to receive e-mail advertising to this address. Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu. (R)etry, (A)bort, (C)ancer -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: why is grep behaving this way ?
On 3/2/07, Matus UHLAR - fantomas [EMAIL PROTECTED] wrote: I'd say that logname detects logged user by checking terminal of stdin file handle... Yup: $ echo | strace -o'|grep readlink' logname readlink(/proc/self/fd/0, pipe:[5242235], 511) = 14 $ strace -o'|grep readlink' logname readlink(/proc/self/fd/0, /dev/pts/7, 511) = 10 -- Michael A. Marsh http://www.umiacs.umd.edu/~mmarsh http://mamarsh.blogspot.com -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: why is grep behaving this way ?
Yes, There are lots of alternatives like : who | grep `id -un` who | grep bhasker or even i tried to do this !!! who a grep `logname` a that WORKS ONLY this command who | grep `logname` does not work ! WHY ? On Fri, 2007-03-02 at 12:16 +0200, Salvatore Iovene wrote: On Fri, Mar 02, 2007 at 03:07:37PM +0530, Bhasker C V wrote: [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. Weird. Consiedering that this works: who | grep `whoami` Where's the catch? -- Bhasker C V Registered Linux user: #306349 (counter.li.org) The box said Requires Windows 95, NT, or better, so I installed Linux. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Re: why is grep behaving this way ?
Bhasker C V wrote:
Yes,
There are lots of alternatives
like :
who | grep `id -un`
who | grep bhasker
or even i tried to do this !!!
who a
grep `logname` a
that WORKS
ONLY this command who | grep `logname` does not work !
WHY ?
Most likely because logname misbehaves when stdin is not a tty.
Mike
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Re: why is grep behaving this way ?
On Fri, Mar 02, 2007 at 04:37:37AM EST, Bhasker C V wrote: I have logname command give me this output [EMAIL PROTECTED] ~]$ logname bhaskerv and say i execute this command [EMAIL PROTECTED] ~]$ echo `logname` bhaskerv till this it is all fine BUT [EMAIL PROTECTED] ~]$ who | grep `logname` logname: no login name Usage: grep [OPTION]... PATTERN [FILE]... Try `grep --help' for more information. is there anything i am doing wrong ? bash man page: Each command in a pipeline is executed as a separate process (i.e., in a subshell). The problem appears to be that the subshell where `logname` executes is not a login shell. Here are a few commands I issued from the linux console that may help clarify: $ logname myuser $ logname 12 | logname # redirect stdout to stderr myuser # 1st instance of logname logname: no login name # 2nd instance of logname The 1st logname command is successful. The 2nd logname command executes in a subshell and returns the message you reported. $ logname | logname 2 /dev/null # returns nothing The 2nd instance of logname writes an error message to stderr and nothing to stdout. As a result, $ who | grep `logname` ends up as: $ who | grep .. resulting in a syntax error. Another angle of approach is that the logname command can only return the login name as long as the calling process added an entry to the utmp file (see info coreutils logname) .. If not, it fails and displays the logname: no login name message. I guess it would not make much sense having all subshells invoked during an interactive session create/remove entries to/from the /var/run/utmp file. Thanks, cga -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
