Interactive input and for statement (8-15)
Interactive input
1, read Usage: The read command can define multiple variable values at the same time, and the input content can be used as the allocator by default to enter the value into the corresponding variable; if the default value is too much, all the values will be assigned to the last variable< /p>
2. If the default is too few, the extra variables will be empty.
3. Example read abc aa bb cc
4. How to enter Read: echo “Please enter a directory” (we need echo- nCancel line breaks)
Echo “Please enter a directory:” read variable (please enter a directory/etc)
5, Common parameters: -p Example: read -p “Please enter a directory” variable
-t: Define the timeout time Example: read -t 5 -p “Please enter a directory:” Variables
6, script default values:
Exercise:
Enter a device file , Output the basic information of this device file.
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#!/bin/ bash #Input a device file, and output the basic information of the device file. read -t 5 -p "Please enter a device file name:" devname code> [ -z $devname] && devname=` fdisk -l` if < code class="bash plain">[ -b /dev/ $devname ]; then fdisk -l /dev/ $devname else fi |
Execution result:
7. Syntax format of case statement:
case variable in
PATTEN1)
Code block 1
;;
PATTEN2)
Code Block 2
;;
*)
Code Library
esac
For statement loop
1. Application scenario: There is a function that needs to be executed in a loop, but the loop object is different, but The loop object is the same kind of data
2, for statement format:
for variable in list; do
loop body
Done
3, echo command parameters: -e: enable the echo command to recognize special characters
: carriage return without line feed
: New line and the cursor moved to the beginning of the line
output >
4. How the list is generated: 1. Give a list of characters directly (for i in abcdef;do)
2. List of integers a{start....end}
p>
b seq command reference $ (seq [start [step]] end)
(seq most common features is the step size)
3 , The command to return to the list (example: $(command))
4. glob mechanism-the mechanism of file name wildcards
: variable application ---- [email] protected] $*Use parameters as a list of for loops
$0 is different from awk. The $0 in bash represents the script file to run
The $0 in Awk represents the entire line of content-awk is executed by line
Use "[email protected]" when multiple words are needed, and "$" when one word is needed
5. Common usage of vim: In command mode, dd means cut, yy means copy, and p means paste
6. Summary of test commands: 1. The parameters of the test command -a, -o only Used in commands; Note: Regular expressions and wildcards are not supported when doing character matching.
2. test test==[[]], when connecting two test commands, you cannot use the command inside The parameters -a, -o are generally used || && == != >= <=
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#!/bin/bash #Input a device file, output this device Basic information of the file. read -t 5 -p "Please enter a device file name:" devname code> [ -z $devname] && devname=` fdisk -l` if < code class="bash plain">[ -b /dev/ $devname ]; then else fi |
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#!/bin/bash #Input a device file, output the device file Basic Information. read -t 5 -p "Please enter a device file name:" devname code> [ -z $devname] && devname=` fdisk -l` if < code class="bash plain">[ -b /dev/ $devname ]; then else fi |
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#!/bin/bash #Input a device file, output this device file Basic information. read -t 5 -p "Please enter a device file name:" devname code> [ -z $devname] && devname=` fdisk -l` if < code class="bash plain">[ -b /dev/ $devname ]; then fdisk -l /dev/ $devname exit 0 < div class="line number9 index8 alt2"> else