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(9) Redirection and Pipes

File Redirection and Pipes

Programs send send output to the screen, standard output, stdout; and programs accept input from the keyboard, standard input, stdin
Redirection operators (<,>) and Pipes (|) change where stdin and stdout go
> - Takes the output of a command/program and send it to a file, ls -la > list_file
< - Directs a file to standard input, mail unix10 < list_file
>> - Will append to a file, note that > will overwrite a file
Redirection operators are good for capturing output from commands and creating files with shell scripts
The pipe operator | takes the output (stdout) of one command and makes it the standard input (stdin) of another command, connects commands together
ls -la | mail joe.the.smith@dartmouth.edu will take the output of the ls command and "pipe" it into the mail command; cat /etc/passwd | wc will send all the lines of the password file to wc (word count)
tee - Displays input and writes it out to a file, good for verifying arguments; find /usr -name README -print | tee to_read

slide09.src last modified Feb 8, 2011

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