Linux Learning essay-shell basic knowledge

1: User's shell History command saved in Home/username/.bash_history

#!! execute the user's previous command #! PW executes the last command in the command history that begins with PW 2: ' * ' to match 0 or more characters '? ' Match one character #ls-D day* lists the directories that start with day and match all characters later #ls-D day? Lists the directory at the start of day, followed by a character 3:>> Append redirect in file > Redirect in Files 4:| Pipe character #cat/etc/passwd|wc-l the output of the CAT/ETC/PASSWD directive is used as input to the WC command. The number of rows that count passwd 5 Ctrl + Z command to pause a task #jobs can view the paused tasks as follows: (my-env) [[email protected] linux_learn]$ jobs [1]+ Stopped vim Test1.txt #fg +id can resume operation #bg +id can put this task in the background run #ps aux |grep test1 can view the PID of the running process in the background #kill-9 PID can end this process 6 $PATHPath When you enter a command, Linux looks for the path that is recorded in path. For example, in the root directory/below you can enter the command LS, you can also enter LS in the/usr directory, but in fact ls This command is not at all in this two directory. in fact, when you enter the command, Linux will go to the/bin,/usr/bin,/sbin and other directories to find the command you entered at this time, and the value of path is exactly the/bin:/sbin:/usr/bin: the colon separates the directory from the directory. 7 SET command can display the system preset variables such as path home, you can also display the user's own defined variables #myname =aming Setting custom variables #set |grep myname myname=aming You can view the variables that you define #bash into another shell. #set |grep myname cannot see the variables we define, the defined variables exist only in the defined shell . 7.1 allow defined variables to be used by all users #sudo Vim/etc/profile Add Export myname=aming #source/etc/profile Effective 7.2 Let the defined variables take effect in all child shells #abc =123 #export ABC 7.3 Canceling a variable unset #unset ABC #unset myname 8 WC Command # wc/etc/passwd-l Count rows # wc/etc/passwd-m Count characters # wc/etc/passwd-w Number of statistical words 9 ~ Indicates the user's home directory Root under the/root Normal user under/home/username 2> indicates error redirection 2>> indicates error append redirect #ls aaaa 2>/tmp/error #ls aaaa 2>>/tmp/error You can view errors in error            

Linux Learning essay-shell basic knowledge