Added information on > >> and | (#19178)

Created a file discussing I/O redirection using pipes and flow control codes for chaining bash commands.

client/src/pages/guide/english/bash/bash-redirection/index.md

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+---
+title: Bash Redirection
+---
+
+## Bash Redirection
+One of the most powerful features of bash (and other shells that support similar syntax) is output and input redirection via pipes and concatination symbols. To start simply the problem of appending a sting to a file is considered. One could open the file in a terminal based editor such as Vim or Nano and manually paste the line in, though this is a bit tedious. Further more, what if one wanted to take the output of one command, say ' $echo 'hi' ' and put it into a file? Again, this could be done via a copy and paste, though this would get progressively more tedious if it had to be done repeatedly and this is not scriptable or automateable so insead something like the '>' or '>>' symbols can be used. With the previous examlpe this may look like:
+
+echo 'hi' > output.txt
+or
+echo 'hi' >> output.txt
+
+The difference between the two is a single '>' will overwrite the destination file with the input while a '>>' will append the input to the destinion file. Interestingly, the destination need not be a file for example say you had a simple program 'add' which takes two, comma delimited integers as input from the user and output the sum. Normally runnig 'add' would wait for input from the user though using a file that contains valid input this could be automated. Say "input.txt" is a text file containing "1,2" running:
+
+input.txt > add
+
+should output '3'
+
+Finally, and most powerful of all, is the pipe "|" which can be used to take a running programs output and 'pipe' it into another program. For example:
+
+sort textfile.txt | uniq
+
+will first sort each line in the file alpahabetically and then print only the unique entries. This is only scratching the surface of the massive power of pipes though.