Commands using egrep (220)

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Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

Create a backup of the file.
It will create a backup of the filename. The advantage is that if you list the folder the backups will be sorted by date. The command works on any unix in bash.

Create more threads with less stack space
default stack size is 10M. This makes your multithread app filling rapidly your memory. on my PC I was able to create only 300thread with default stack size. Lower the default stack size to the one effectively used by your threads, let you create more. ex. putting 64k I was able to create more than 10.000threads. Obviously ...your thread shouldn't need more than 64k ram!!!

Watch the progress of 'dd'
Only slightly different than previous commands. The benefit is that your "watch" should die when the dd command has completed. (Of course this would depend on /proc being available)

Find top 5 big files
zsh: list of files sorted by size, greater than 100mb, head the top 5. '**/*' is recursive, and the glob qualifiers provide '.' = regular file, 'L' size, which is followed by 'm' = 'megabyte', and finally '+100' = a value of 100

check open ports without netstat or lsof

Count number of files in a directory

Indent a one-liner.
Bash builtin type also indents the function.

Short one line while loop that outputs parameterized content from one file to another
The above is an example of grabbing only the first column. You can define the start and end points specifically by chacater position using the following command: $ while read l; do echo ${l:10:40}; done < three-column-list.txt > column-c10-c40.txt Of course, it doesn't have to be a column, or extraction, it can be replacement $ while read l; do echo ${l/foo/bar}; done < list-with-foo.txt > list-with-bar.txt Read more about parameter expansion here: http://wiki.bash-hackers.org/syntax/pe Think of this as an alternative to awk or sed for file operations


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