Shell Usage Tips

Skillfully using the delimiter delimiter

Where to enter large pieces of text

Automatic selection and entry of places

Accessing the database

[Email protected] ~cat > OUT.txt << EOF> 123jl412 3> o> EOF

Tool Usage Tips

Uniquely identifies

Date: Creates a log file as a file name using the date command.

$$: Creates a unique temporary file with the process number.

Send Signal

Signal	Signal Name	Meaning
0	EXIT	Exit signal (using exit, ctrl-d can be issued)
1	SIGHUP	Hangs or the parent process is killed
2	SIGINT	Interrupt signal from the keyboard, usually <CTRL-C>
3	Sigquit	Exit from keyboard
9	SIGKILL	Unconditional termination
11	SIGSEGV	Segment (memory) conflict
15	SIGTERM	Software termination (default kill process signal)

The signal can be sent using the following format (the default is 15):
Kill [-signal no:| signal name] process ID

You can use KILL-L to list all signals

Detection signal

Traps allow you to capture signals in the script. The general form of the command is:
Trap name Signal (s)

Common use of TRAP commands

Trap "" 2 3	Ignoring signal 2 and signal 3, the user cannot terminate the script
Trap "Commands" 2 3	If the signal 2 or 3 is captured, the corresponding commands command is executed
Trap 2 3	Reset signals 2 and 3, the user can terminate the script

Eval

Use the eval command to execute the command after the eval command.

Logger

Using the Logger command, you can write log to the message in the system's log directory (view/etc/syslog.conf's system settings).

The general form of the Logger command is:
Logger-p-I. Message

P is the priority, I is the process number

Shell Usage Tips