Linux Shell sleep/wait (reprint)

Linux Shell sleep/wait (reprinted) 2007-04-27 18:12

Bash's basic configuration is made up of configuration files./etc/profile is called a global configuration file for the shell.
Another file in the personal directory under the personal directory/.bash-profile
There's a file in the personal directory./ETC/BASHRC is the second global profile, which holds (function aliases, etc.) also has a configuration file in the personal directory ~/.BASHRC
Environment variable: variable name = variable Value example: Lang=en is set language to English
LANG=ZH-CN.GB18030 is set language to Chinese
Value of reference variable: $ variable Name example: Export path= $PATH:/etc/xxx
For example: Echo $LANG echo echoing command to see the value of LANG
Example Export CMD =ls
$CMD –l equals Ls–l.
Output redirection: (1) name > filename The original command to output to the terminal is changed to output to a file
(This is called overlay redirection)
(2) Name >> file name
(add-on redirection)
Example: GCC command 0: standard input
1: Standard output
2: Standard error output

(3) Pipeline Unix traditional inter-process communication notation: Command 1 | Command 2
More or grep is often present at command 2.
Example: Cat/etc/services | grep ' http ' means an output that contains HTTP
Jinscan

Shell script: It is composed of shell commands, small-scale, structured, modular, program design. Command: Echo output information with
Read input information read variable name
Sleep sleeps sleep seconds
Arithmetic expression on Terminal: Echo $ ((1x2x3)) This is an integer operation with no decimal points.
/: Except
%: Remainder
Shell Script format:
The first line must be #!. /bin/sh
There are three structural sequential structure of the branching structure circular structure
Sequential structure
The wait command ensures that the process is waiting synchronously for a child process to end multiple concurrency with multiple wait
Example: #! /bin/sh
echo "1"
Sleep 5&
echo "3"
echo "4"
Wait
echo "5"
Branching structure

if judgment; Then
T block
Else
Block F
Fi
Judge Test statement Test expression = [expression]
The expression is file-determined-F file name (detects if the file exists and is a normal file
-D directory Name
-R Readable
-W Writable
-X Executable

These examples are due to years of disrepair (incomplete notes, forgotten places) Please forgive me for the error
Example:
            #! /bin/sh
           echo "file"
            read     FileName
            if     [-f $FileName]; Then
                echo "Yes"
             Else
             echo "No"
     fi

string comparison equal String a = string b
Unequal string A! = string B
-Z to determine if the string is zero null for true non-null false

Linux Shell sleep/wait (reprint)