"input and output in product Linux"
Input and output in Linux
Input
Stdin [standard input stream]
Input refers to the information transferred to the system by the external connection of the system
The way in which the system externally transfers data to the system is as follows
1. Keyboard
two。 Mouse
3. Enter a command
Output
Output standout [standard correct input] stderr [standard error output] the string generated after the successful execution of the command, the output signal of the string in linux is 1stderr in linux, the output signal of the string in linux is 2
Character equipment
A character device refers to a device that transmits characters in units during Istroke O transmission, such as keyboards, printers, etc.
A character device is a virtual device that is turned on in memory and is real.
Redirect output find / etc/-name passwd
Note: must be under the ordinary user
1 > 2 > & > correct output, error output, all output
Mini App: > westos clears files
2 find / etc/-name passwd append: do not overwrite the original file
Find / etc/-name passwd > westos.out correct output is stored in westos.out
Additional
Append right / wrong / all
Pipeline
Pipe definition: turn the output into the input of the last command
Symbolic usage 2 > & 1 converts the output numbered 1 to 2lee copy output to the specified location''conduit character
Example: display history 3'5 lines output
[student@workstation Desktop] $ls / bin | wc-l # # Statistics / how many files are there in bin 1612 [student@workstation Desktop] $find / etc/-name passwd | wc-l # # by default only the correct output can be obtained through the pipeline find:'/ etc/pki/rsyslog': Permission deniedfind:'/ etc/dhcp': Permission deniedfind:'/ etc/polkit-1/rules.d': Permission deniedfind:'/ etc/polkit-1/localauthority': Permission deniedfind :'/ etc/sssd': Permission deniedfind:'/ etc/grub.d': Permission deniedfind:'/ etc/audit': Permission deniedfind:'/ etc/firewalld': Permission deniedfind:'/ etc/sudoers.d': Permission deniedfind:'/ etc/lvm/archive': Permission deniedfind:'/ etc/lvm/backup': Permission deniedfind:'/ etc/lvm/cache': Permission deniedfind:'/ etc/libvirt': Permission deniedfind:'/ etc/cups/ssl': Permission denied2 [student@workstation Desktop] $find / etc/-name passwd 2 > & 1 | wc-l # # directs the error output to the correct output location 16 [student@workstation Desktop] $find / etc/-name passwd | tee file | wc-l # copy the output to the file file and count the output through the pipeline find:'/ etc/pki/rsyslog': Permission deniedfind:'/ etc/dhcp': Permission deniedfind:'/ etc/polkit-1/rules .d': Permission deniedfind:'/ etc/polkit-1/localauthority': Permission deniedfind:'/ etc/sssd': Permission deniedfind:'/ etc/grub.d': Permission deniedfind:'/ etc/audit': Permission deniedfind:'/ etc/firewalld': Permission deniedfind:'/ etc/sudoers.d': Permission deniedfind:'/ etc/lvm/archive': Permission-** input redirection
Take changing the password as an example
Enter redirection symbol
Command
