Linux I/O Redirection exec 6<&0 # Link file descriptor #6 with stdin. # Saves stdin. exec < data-file...

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Linux I/O Redirection
exec 6<&0 # Link file descriptor #6 with stdin.
# Saves stdin.
exec < data-file # stdin replaced by file "data-file"

read a1 # Reads first line of file "data-file".
read a2 # Reads second line of file "data-file."

echo "Following lines read from file."
echo $a1
echo $a2

exec 0<&6 6<&-
# Now restore stdin from fd #6, where it had been saved,
#+ and close fd #6 ( 6<&- ) to free it for other processes to use.
# <&6 6<&- also works.
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There are always three default files [1] open, stdin (the keyboard), stdout (the screen), and stderr (error messages output to the screen). These, and any other open files, can be redirected. Redirection simply means capturing output from a file, command, program, script, or even code block ...

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