Commands by mikejmc (1)

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Remove old kernel packages

Find out when your billion-second anniversary is (was).
This is the same command as this one, but for OS X. http://www.commandlinefu.com/commands/view/3053/find-out-when-your-billion-second-anniversary-is-was.

Search some text from all files inside a directory

Get all files of particular type (say, PDF) listed on some wegpage (say, example.com)
See man wget if you want linked files and not only those hosted on the website.

Real full backup copy of /etc folder
Yes, rsync(1) supports local directories. And, should anything change, it's trivial to run the command again, and grab only the changes, instead of the full directory.

Press ctrl+r in a bash shell and type a few letters of a previous command
In the sample output, I pressed ctrl+r and typed the letters las. I can't imagine how much typing this has saved me.

Convert all files for iPhone with HandbrakeCLI

Find brute force attempts on SSHd
Searches the /var/log/secure log file for Failed and/or invalid user log in attempts.

Show IP Address in prompt --> PS1 var
when working with many machines in a computer lab need to know the IP addr is very large, this is a simplistic solution to make things easier

Determine if a command is in your $PATH using POSIX
it is generally advised to avoid using which(1) whenever possible. which(1) is usually a csh(1) script, or sometimes a compiled binary. It's output is highly variable from operating system to operating system, so platform independent scripts could become quite complicated with the logic. On HP-UX 10.20, for example, it prints "no bash in /path /path /path ..."; on OpenBSD 4.1, it prints "bash: Command not found."; on Debian (3.1 through 5.0 at least) and SuSE, it prints nothing at all; on Red Hat 5.2, it prints "which: no bash in (/path:/path:...)"; on Red Hat 6.2, it writes the same message, but on standard error instead of standard output; and on Gentoo, it writes something on stderr. And given all these differences, it's still variable based on your shell. This is why POSIX is king. See http://mywiki.wooledge.org/BashFAQ/081 for more ways on avoiding which(1).

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