Shell review notes ---- user management, shell ---- user management

Shell review notes ---- user management, shell ---- user management

$ Who can know the number of logins to the System

 

$ Who | wc-l: calculate the number of users

Note: | it is a pipeline symbol. pipeline can be established between two programs (pipeline): the output of who is the wc input. The result listed by wc is the number of logged-on users.

The pipeline is converted into an independent command by entering this command into a common file, and then using chmod to set the execution permission for the file.

#! /Bin/sh when a file contains the first two characters #! The kernel will scan the remaining parts of the line to see if there is a complete path available for executing the program's interpretation. the kernel will reference the interpreter with a straight-forward option, and then use the other part of the command line. generally, shell scripts start #! /Bin/sh.

$ Cat> nusers creates a file and uses cat to copy the input from the terminal.

Who | content of the cw-l program

^ D Ctrl-D indicates end-of-file

$ Chmod + x nusers grant the File Execution permission

$./Nusers run the test

6. Possible output test results