Difference between pages "Piping" and "Snmp"

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imported>ThorstenStaerk
(New page: The most fascinating thing about Unix is how the following works together: * the way Unix treats streams * the paradigm "everything is a file" * the paradigm "do one thing and do it well" ...)
 
imported>ThorstenStaerk
 
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The most fascinating thing about Unix is how the following works together:
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Trying to build an SNMP prototype
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* the way Unix treats streams
 
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* the paradigm "everything is a file"
 
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* the paradigm "do one thing and do it well"
 
  
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Let's start with the most basic program: cat. cat inputs a "stream" and outputs a "stream", nothing else. Find it out like this:
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SUSE Linux:
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poochy:~ # cat
 
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Hello, I am typing a line
 
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Hello, I am typing a line
 
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After typing cat with no parameters, you can ''input'' a line (followed by ENTER). cat does nothing but ''output'' the line again. You end your input with CTRL_D. Standard for your input is the keyboard, standard for a program's output is the console.
 
  
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'''''How can this be useful?'''''
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yast -i nagios apache2
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/etc/init.d/nagios start
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http://127.0.0.1/nagios
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log in as nagiosadmin:nagiosadmin
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/etc/init.d/snmptrapd
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tail -f /var/log/net-snmpd.log
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snmptrap -v 2c -c public localhost "" NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatNotification netSnmpExampleHeartbeatRate i 42
  
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This can be extremely useful. E.g. take the paradigm "everything is a file". So you can replace your ''input stream'' by a file using a parameter:
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  No access configuration - dropping trap.
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  cat ''readme.txt''
 
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outputs the content of ''readme.txt'' to the console. So you can display a file.
 
  
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Or you can redirect cat's output ''stream'' to a file using the > operator:
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So it seems I have to  
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cat > myfile.txt
 
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Allows you to (over)write directly the file ''myfile.txt''.
 
  
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Or you can redirect the output of cat to the input of another command using the | (pipe) operator:
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cat /etc/snmp/snmptrapd.conf
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  cat myfile.txt | cat
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  disableAuthorization yes
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is equivalent to cat myfile.txt.
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traphandle default /bin/snmppl
  
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'''''How can this pipe be useful?'''''
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/etc/init.d/snmptrapd restart
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cat /bin/snmppl
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#!/bin/bash
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date >>/tmp/dates
  
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There is a command to search a string in a stream (yes, or in a file, because everything is a file), called grep.
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= See also =
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grep needle
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* http://nagios.sourceforge.net/docs/3_0/quickstart-opensuse.html
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takes an input stream and echos only those lines containing the string "needle":
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* http://net-snmp.sourceforge.net/wiki/index.php/TUT:snmptrap
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poochy:/usr # grep needle
 
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haystack
 
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hay
 
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more hay
 
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even more hay
 
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needle
 
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needle
 
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again hay
 
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some more hay
 
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Now if we combine cat and grep, we get
 
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cat * | grep needle
 
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"*" stands for "all files". This command searches in all files for the string "needle" and outputs the files that contain it. Just FYI, this is equivalent to
 
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grep "needle" *
 
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because, as said, you can hand over files to grep.
 

Revision as of 16:46, 4 April 2014

Trying to build an SNMP prototype

SUSE Linux: 

yast -i nagios apache2
/etc/init.d/nagios start
http://127.0.0.1/nagios

log in as nagiosadmin:nagiosadmin 

/etc/init.d/snmptrapd
tail -f /var/log/net-snmpd.log
snmptrap -v 2c -c public localhost "" NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatNotification netSnmpExampleHeartbeatRate i 42

No access configuration - dropping trap.

So it seems I have to 

cat /etc/snmp/snmptrapd.conf
disableAuthorization yes
traphandle default /bin/snmppl

/etc/init.d/snmptrapd restart
cat /bin/snmppl
#!/bin/bash
date >>/tmp/dates

See also

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