Commands by haivu

This command looks for a single file named emails.txt which is located somewhere in my home directory and cd to that directory. This command is especially helpful when the file is burried deep in the directory structure. I tested it against the bash shells in Xubuntu 8.10 and Mac OS X Leopard 10.5.6

The socket.gethostname() call returns the host name of the computer. The socket.gethostbyname_ex() call returns a list of three items: The host name, the list of aliases for this host, and a list of IP addresses. Recall that Python?s array starts with index 0, the socket.gethostbyname_ex(?)[2] expression refers to the list of IP addresses. Finally, the print statement prints out the IP addresses, one per line.

After seeing the command you wish to repeat, just invoke it using the ! syntax.

Shows all linked file and destinations. The 'ls -l' command lists the files in long (1 file per line) format, and the grep command displays only those lines that starts with an l (lower case L) -- a linked file.

Updated: Remove reference to hard links because this command does not apply to hard link as others kindly pointed out.

the -3 show the previous, current, and next month.

The whatis command displays a short description for the command you list on the command line. It is useful to quickly learn what a command does

bc is a wonderful calculator. Just type bc at the command line and have at it. Ctrl+D (or type quit) will get you out. This usage is just scratching the surface: bc can handle a mini scripting language, complete with variable, statements, loop, conditional statements and more. Do a man page on it to find out.

Short and sweet command. This command is also useful for other information such as what IP address a particular user logged in from, how long had they been logged in, what shell do they use.

bvi is your vi for binary editing. If your system does not have it, you can get it from

http://bvi.sourceforge.net/

The brace expansion also allows you to count backward:

for i in {15..1}; do echo $i; done

You can also use this construct to create new file or new directory:

mkdir dir{1..3} # Same as mkdir dir1 dir2 dir3

I often deal with long file names and the 'ls -l' command leaves very little room for file names. An alternative is to use the -h -o and -g flags (or together, -hog).

* The -h flag produces human-readable file size (e.g. 91K instead of 92728)

* The -o suppresses the owner column

* The -g suppresses the group column

Since I use to alias ll='ls -l', I now do alias ll='ls -hog'

If you would like to edit a previous command, which might be long and complicated, you can use the fc (I think it stands for fix command). Invoke fc alone will edit the last command using the default editor (specified by $FCEDIT, $EDITOR, or emacs, in that order). After you make the changes in the editor, save and exit to execute that command. The fc command is more flexible than what I have described. Please 'man bash' for more information.

CDPATH tells the cd command to look in this colon-separated list of directories for your destination. My preferred order are 1) the current directory, specified by the empty string between the = and the first colon, 2) the parent directory (so that I can cd lib instead of cd ../lib), 3) my home directory, and 4) my ~/projects directory.

The output of "echo $PATH" is hard to read, this is much easier. The parentheses ensure that the change to the input field separator (IFS) only happens the the sub shell and not affecting the current shell.

over works like 'more' or 'less', but it pretty print the source code

If you spend most of your time in front of the terminal, leave is a useful reminder. Leave can have absolute form: leave 1555 reminds you to leave at 3:55PM

This command is almost the same as 'ls -a', but it does not display the current dir (.) or parent (..)

Listen to different voices in the system--useful for picking the voice you like

I put that line in my .bash_profile (OS X) and .bashrc (Linux).

Here is a summary of what the \char means: n=new line, u=user name, h=host, !=history number, w=current work directory

The \[\e[32m\] sequence set the text to bright green and \[\e[0m\] returns to normal color.

For more information on what you can set in your bash prompt, google 'bash prompt'

Often, the very next command after the cd command is 'ls', so why not combine them?. Tested on a Red Hat derivative and Mac OS X Leopard

Update: changed ${1:-$HOME} to "${@:-$HOME}" to accomodate directories with spaces in the names

The -R flag prevents you from making changes to a file, useful when you only want to view the file. This command is nicer than the 'more' or 'less' commands because for source codes, vi shows syntax highlight.

Explanation:

* The date command evaluated to today's date with blank padded on the left if single digit

* The grep command search and highlight today's date

* The --before-context and --after-context flags displays up to 6 lines before and after the line containing today's date; thus completes the calendar.

I have tested this command on Mac OS X Leopard and Xubuntu 8.10

Waiting for your server to finish rebooting? Issue the command above and you will hear a beep when it comes online. The -i 60 flag tells ping to wait for 60 seconds between ping, putting less strain on your system. Vary it to your need. The -a flag tells ping to include an audible bell in the output when a package is received (that is, when your server comes online).

On Linux and Mac systems (I have not tested with other Unix systems), the ping command will keep on pinging until the user interrupts it with Ctrl+C. On Windows system, ping will execute for a number of times then quit. The -c flag on Linux and Mac will make this happen

Place the line above in your ~/.bahsrc file. Now every time you issue the 'vb' command, you invoke the vim editor to edit it, then source it so the changes take effect immediately.

Notes:

* This mechanism is not working well if your .bashrc contains commands that should not be sourced more than once.

* This trick also work for your csh or tclsh users: place the following line in your ~/.cshrc file:

alias vc 'vim ~/.cshrc; source ~/.cshrc

Thank you adzap for pointing out the missing quote