Understanding these redirection operators is crucial to understanding the kinds of wizardly command lines you're presumably here to learn. Pipe the standard output of the thing on the left into the standard input of the thing on the right.Įcho "test123" | mail -s "subjectline" emailaddress Ls /home/me > myfilestwice.txt ls /home/me > myfilestwice.txt Ls /home/me > myfilesonce.txt ls /home/me > myfilesonce.txtĪppend the output of the thing on the left to the end of the existing file on the right. Place the output of the thing on the left in the empty file named on the right. Process the command on the right after you're done processing the command on the left. Again, we're going to keep this very simple: Operator Redirection 101īefore we can talk about sed, awk, and grep, we need to talk about something a bit more basic-command-line redirection. Instead of giving you encyclopedic listings of every possible argument and use case for each of these ubiquitous commands, we're going to teach you how to think about them-and how to easily, productively incorporate them in your own daily command-line use. If you find yourself in the same boat, grab a beverage and buckle in. For example, the sed man page weighs in at around 1,800 words alone without ever really explaining how regular expressions work or the most common uses of sed itself. Trying to read the man pages for the utilities most frequently seen in these extended command chains didn't make them seem more approachable, either. Surely, this was just an exercise in e-braggadocio, right? Honestly, I doubted the real-world value of that. Authors and commenters might chain 10 commands together with pipes and angle brackets-something I never did in day-to-day system administration.
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