| Shell metacharacters > Prog> file redirects the standard output to the file
> Prog> file: attaches the standard output to the file.
<Prog <file: Get standard input from File
| P1 | P2 uses the P1 standard output as the P2 standard input
<String here document: the standard input is read from here document until a string is displayed.
* Match zero or multiple characters in the file name
? Match any single character in the file name
{ABC} matches any characters in the ABC range in the file name, for example, 0-9 or a-Z.
Command Terminator, for example, P1; P2 indicates that P1 is executed first, and then P2 is run
& Command Terminator, similar to;, but not equal to p1
'...' Run the command in... and the output result replaces '...'
(...) Execute the command in the sub-shell...
{...} Execute the command in... in the current shell (rarely used)
$1, $2, etc. $0... $9 represents the parameters of the shell file
$ Variable shell variable value
$ {Variable} variable value to avoid confusion during text connection
// C uses the C character as the character, but the/line break is invalid.
'...' As text, no replacement
"..." In..., $, '...' and/are replaced, and then... is used as the text.
# Annotation
Variable = value: variable value
P1 & p2 run P1; if successful, run P2 again
P1 | P2 run P1; if it fails, run P2 again
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Shell internal variables $ # number of parameters, starting from 0
$ * all shell parameters
$ @ similar to $ *, for more information, see Article http://bbs.chinaunix.net/viewthread.php? Tid = 218853 & extra = & page = 7
$-Options for shell
$? Returned value of the last command
$ $ shell process identifier
$! Use the process identifier of the last & started command
$ Home CD default parameter
$ ifs parameter to separate the two-dimensional table of words
$ mail file, when it changes, You have mail... you have never used this ^ _ ^
$ path to search for the Directory table
$ PS1 prompt string. The default value is $ |
