I/O Redirection: how can I redirect error msgs to a temp file Post: 302486224

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Top Forums Shell Programming and Scripting I/O Redirection: how can I redirect error msgs to a temp file Post 302486224 by DGPickett on Friday 7th of January 2011 12:21:50 PM

01-07-2011

Registered User

Some messages are on stdout (1), some on stderr (2) (in bits!), none on /dev/tty, for my HPUX system:

Code:

$ truss -o /tmp/nsl.tr nslookup 12.23.34.45 ; grep write /tmp/nsl.tr          
Using /etc/hosts on:  hideme
looking up FILES
Trying DNS
Trying NIS
*** No hostname information is available for "12.23.34.45"
write(1, "U s i n g   / e t c / h o s t s ".., 32) ....... = 32
write(1, "l o o k i n g   u p   F I L E S ".., 17) ....... = 17
write(1, "T r y i n g   D N S \n", 11) ................... = 11
write(1, "T r y i n g   N I S \n", 11) ................... = 11
write(2, "* * *   N o   h ", 8) .......................... = 8
write(2, "o s t n a m e ", 7) ............................ = 7
write(2, "  i n f o r m a ", 8) .......................... = 8
write(2, "t ", 1) ........................................ = 1
write(2, "i o n   i s   a ", 8) .......................... = 8
write(2, "v ", 1) ........................................ = 1
write(2, "a i l a b l e   ", 8) .......................... = 8
write(2, "f ", 1) ........................................ = 1
write(2, "o r   " 1 2 . 2 ", 8) .......................... = 8
write(2, "3 . 3 4 . 4 5 ", 7) ............................ = 7
write(2, "" \n", 2) ...................................... = 2
$ 
 
 
 
Good IP:
 
$ truss -o /tmp/nsl.tr nslookup 89.67.45.123 ; grep write /tmp/nsl.tr
Using /etc/hosts on:  hideme
looking up FILES
Name:    hideme
Address:  89.67.45.123
Aliases:  hideme.somedomain.com
write(1, "U s i n g   / e t c / h o s t s ".., 32) ....... = 32
write(1, "l o o k i n g   u p   F I L E S ".., 17) ....... = 17
write(1, "N a m e :         h i d e m e \n".., 26) ....... = 26
write(1, "    8 9 . 6 7 . 4 5 . 1 2 3 ".., 26) ....... = 26
write(1, "    h i d e m e . s o m e d o ".., 34) ....... = 34
$
 
 
Good IP, PTR specific query for pointer-reverse = ip to name:
 
$ truss -o /tmp/nsl.tr nslookup -q=PTR 89.67.45.123 ; grep write /tmp/nsl.tr
Using /etc/hosts on:  hideme
looking up FILES
Trying DNS
123.45.67.89.in-addr.arpa    name = hideme.somedomain.com
write(1, "U s i n g   / e t c / h o s t s ".., 32) ....... = 32
write(1, "l o o k i n g   u p   F I L E S ".., 17) ....... = 17
write(1, "T r y i n g   D N S \n", 11) ................... = 11
write(1, "1 2 3 . 4 5 . 6 7 . 8 9 . i n - ".., 28) ....... = 28
write(1, "\tn a m e   =   h i d e m e . s ".., 34) ....... = 34
write(1, "\n", 1) ........................................ = 1
$
 
 
Good IP, specific DNS server:
 
$ truss -o /tmp/nsl.tr nslookup 89.67.45.123 89.123.45.67 ; grep write /tmp/nsl.tr 
Name Server:  nameserver1.somedomain.com
Address:  89.123.45.67
Trying DNS
Name:    hideme.somedomain.com
Address:  89.67.45.123 
write(1, "N a m e   S e r v e r :     n a ".., 50) ....... = 50
write(1, "    8 9 . 1 2 3 . 4 5 . 6 7 \n".., 17) ....... = 17
write(1, "T r y i n g   D N S \n", 11) ................... = 11
write(1, "N a m e :         h i d e m e ".., 44) ....... = 44
write(1, "    8 9 . 6 7 . 4 5 . 1 2 3 ".., 19) ....... = 19
$

Tools like this, called truss, tusc or strace, can tell you what you are seeing in more detail.

Last edited by DGPickett; 01-07-2011 at 01:44 PM..

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LEARN ABOUT LINUX

bsd-write

WRITE(1)						    BSD General Commands Manual 						  WRITE(1)

NAME

     write -- send a message to another user

SYNOPSIS

     write user [tty]

DESCRIPTION

     The write utility allows you to communicate with other users, by copying lines from your terminal to theirs.

     When you run the write command, the user you are writing to gets a message of the form:

	   Message from yourname@yourhost on yourtty at hh:mm ...

     Any further lines you enter will be copied to the specified user's terminal.  If the other user wants to reply, they must run write as well.

     When you are done, type an end-of-file or interrupt character.  The other user will see the message 'EOF' indicating that the conversation is
     over.

     You can prevent people (other than the super-user) from writing to you with the mesg(1) command.

     If the user you want to write to is logged in on more than one terminal, you can specify which terminal to write to by specifying the termi-
     nal name as the second operand to the write command.  Alternatively, you can let write select one of the terminals - it will pick the one
     with the shortest idle time.  This is so that if the user is logged in at work and also dialed up from home, the message will go to the right
     place.

     The traditional protocol for writing to someone is that the string '-o', either at the end of a line or on a line by itself, means that it is
     the other person's turn to talk.  The string 'oo' means that the person believes the conversation to be over.

SEE ALSO

     mesg(1), talk(1), wall(1), who(1)

HISTORY

     A write command appeared in Version 1 AT&T UNIX.

BUGS

     The sender's LC_CTYPE setting is used to determine which characters are safe to write to a terminal, not the receiver's (which write has no
     way of knowing).

     The write utility does not recognize multibyte characters.

BSD
								   July 17, 2004							       BSD