1. Definition of input and output
1 Input: It is our keyboard, mouse and the characters we use to enter in the system
2 Output: After the system receives the function characters we want to implement, the characters are processed and produced by the system. There will be two kinds of input: the number 1 is the correct output, the number 2 is the error output, by default both outputs will be directed to the character device by the system
2. How to manage output
1. Non-interactive multi-line entry
vim C_pass.sh
passwd
sh C_pass.sh
does not run automatically
passwd <<EOF
chcshidewu
dhwjefffe
EOF
sh C_pass.sh
Can run automatically to avoid interaction
2. How to manage output redirection
> redirect correct output
2 > redirect error output
&> redirect all output
2>&1 converts the error output number from 2 to 1
Do the following experiments with the student user
find /etc/ -name passwd > file.out
find /etc/ -name passwd 2> file.out
find /etc/ -name passwd &> file.all
find /etc/ -name passwd > file 2>&1
"Note: Slave orientation will overwrite the original file content!!!"
vim westos
hello westos
find /etc/ -name passwd > westos
The content of the original file of cat westos is gone
3. Append: Append the output to the file while keeping the contents of the original file unchanged
>> append to correct output
2 >> append to error output
&>> append to all outputs
find /etc/ -name passwd >> westos
find /etc -name passwd 2>> westos
find /etc -name passwd &>> westos
4. Pipeline: The input pipeline that turns the output into the next program is used to combine multiple commands.
ls /bin | wc -l
"Note: The output will become input after passing through the pipeline, so it cannot be saved in the file"
tee ##Copy the output to the specified location
ls /bin | tee file | wc -l
The output has been saved in cat file ##file
