Redirection is a function common to most command-line interpreters, including various unix shells that can redirect standard streams to user specified locations.
UNIX STANDARD I/O Streams
0- stdin (Standard input)
1- stdout (Standard output)
2- stderr (standard error)
Redirecting standard input and standard output
simple redirection to a file: $command > file
redirection & appending to a file: $command >> file
Redirecting to and from the standard file handles
eg: $ command 2> file
executes the command & redirects standard error to file.
Merging of standard error into standard output can be obtained by
eg: $ find / -name .profile > results 2>&1
Redirect to multiple outputs
The standard command “tee” can be used to redirect output from a command to several destinations
eg: $ ls -lrt | tee xyz
this redirects the file list output to both “standard output” and “file xyz”.