http://zort.org/tips.zunix.org Tips that I collected & invented. Thu, 03 Dec 2009 08:30:26 +0000 http://backend.userland.com/rss092 en :%s/^M//g or :set ff=unix http://zort.org/tips.zunix.org/?p=79 MTU: Maximum Transfer Unit. It is calculated in bytes. For example, commonly for ethernet devices the MTU is set to 1500. MTU is set in the device configuration settings for Ethernet, Token ring etc. == In computer networking, the term Maximum Transmission Unit (MTU) refers to the size (in bytes) of the largest ... http://zort.org/tips.zunix.org/?p=78 In computer sciece: 2^10 = 1,024 * the digital approximation of the kilo-, or 1,000 multiplier, which causes a change of prefix. For example: 1,024 bytes = 1 kilobyte (or kibibyte). * This number has no special ... http://zort.org/tips.zunix.org/?p=77 Here it is: tcpdump tcp[13] == 2 Here, tcp[13] contains the value of the 13th octet in the TCP header. And, to match only SYN packets, this value must be equal to 2 when interpreted as a 8-bit unsigned integer in network byte order. Follow-up question: what would be the tcpdump format to ... http://zort.org/tips.zunix.org/?p=76 Here is the command: tcpdump ‘icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply’ http://zort.org/tips.zunix.org/?p=75 To turn off bell: xset -b b off To turn it back on: xset -b b http://zort.org/tips.zunix.org/?p=74 Two ways: using ‘expr’ or ${#variable}. Example: zia@lappy:~$ string=supercalifragilisticexpialidocious zia@lappy:~$ echo ${#string} 34 zia@lappy:~$ expr length $string 34 zia@lappy:~$ expr “$string” : ‘.*’ 34 zia@lappy:~$ expr match “$string” ‘.*’ 34 Source: http://www.tldp.org/LDP/abs/html/string-manipulation.html http://zort.org/tips.zunix.org/?p=73 # Comments. (with exception of “#!”). ; Command separator (semicolon). ;; Terminator in a ‘case’ option (double semicolon) . “dot” command (period). Equivalent to “source;” or “dot” as a componant of a filename or “dot” character match in regular expression. “ partial quoting (double quote) ‘ full quoting (single ... http://zort.org/tips.zunix.org/?p=71 Mostly in linux: route -rn Almost all *nix: netsat -rn http://zort.org/tips.zunix.org/?p=70 Single quote: variables ($), backticks (“) & backslash (\) are not treated specially in single quote. Example: zia@lappy:~$ echo ‘$(ls -al t*)’ $(ls -al t*) zia@lappy:~$ echo ‘`ls -lah t*`’ `ls -lah t*` zia@lappy:~$ echo ‘`ls -lah t*` \”‘ `ls -lah t*` \” Synopsis: with single-quote, the special characters (i.e. $, “, \ etc.) are not treated specially, ... http://zort.org/tips.zunix.org/?p=69