Lec. 10 Standard Text Streams and Redirection

Standard Out
• When a command executes without any errors, the output produced is known as standard out (also called stdout or STDOUT) • By default stdout is sent to the terminal • You can redirect stdout from a command into a file
Standard Out
• To redirect stdout of a command to a file, use the “>”: $ls > /tmp/ls.txt • A single > will override existing file contents • Use >> to append to the end of a file • Stdout is assign a numeric value of 1, so it could also be used like this: $ls 1> /tmp/ls.txt
Standard Error
• When command encounters an error, it will produce output that is known as standard error (also called stderr or STDERR). • The stderr output is sent to the terminal • The number associated with the standard error file descriptor is 2.
Standard Error
To redirect stderr, use the following syntax: $ls /junk 2> /tmp/output.err • A single 2> will override existing file contents • Use 2>> to append to the end of a file • To discard output, redirect output to the /dev/null file (trash can)