Use of variables in the shell (2)

Some knowledge of variables in the shell:

Variable:

1. By default, all variables are considered to be stored as strings.

2. Variable case sensitivity

3. Add $ to the variable name before accessing the content

4. No declaration required

5. The $ extension is allowed in double quotes (replaced with the value of the variable), and the single quotation mark does not work.

Example:

S=hello # (Note that no spaces are allowed on both sides of the equals sign)

Echo $s

Environment variables:

When the shell script starts executing, some variables are initialized according to the values in the environment settings, which are environment variables. Get used to capital letters.

$HOME the home directory of the current user

$PATH a colon-separated list of directories to search for commands

The name of the shell script

$# the number of arguments passed to the script

$$ the process number of the shell script

3. Parametric variables

If the script is run with parameters, these parameter variables are created

$1,$2. Parameters of a script program

$* all the parameters to TFS to separate

[email protected] parameters are not squeezed together by $* variants

Use of variables in the shell (2)