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Print one . instead of each line
this version only uses shell builtins

If (and only if) the variable is not set, prompt users and give them a default option already filled in.
The read command reads input and puts it into a variable. With -i you set an initial value. In this case I used a known environment variable.

Less a grep result, going directly to the first match in the first file
Really useful way to combine less and grep while browsing log files. I can't figure out how to make it into a true oneliner so paste it into a script file called lgrep: Usage: lgrep searchfor file1 [file2 file3] Advanced example (grep for an Exception in logfiles that starts with qc): lgrep Exception $(find . -name "qc*.log")

Create a 5 MB blank file via a seek hole
Similar to the original, but is much faster since it only needs to write the last byte as zero. A diff on testfile and testfile.seek will return that they are the same.

Shortcut to find files with ease.
It looks for files that contains the given word as parameter. * case insensitive * matches files containing the given word.

Remove all the files except abc in the directory
Finds all files in the current directory and deletes them besides file called "abc"

Add a line from 1 file after every line of another (shuffle files together)
After every line in targetfile (empty lines included) insert in a line from addfile. "Save" results to savefile. Addfile should be longer than targetfile since this doesn't loop back to the top of addfile. /^/R addfile -- says for every line that matches "has a start of line" output a line from the file addfile. > savefile (optional) -- redirect output to savefile file.

Calculate days on which Friday the 13th occurs
I removed the dependency of the English language

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"

convert binary data to shellcode


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