Linux Basic Tutorial 45-read command

Basic usage

? ? The read command is primarily used to read from or read from a standard input, and to save the information to a variable. Its common usage is as follows:

read [选项] [文件]

Options	explain
-A array	Reads content into numeric values, variable defaults to array and spaces as delimiters
-D delimiter	Stop reading if the specified character is encountered
-N Nchars	Specifies the maximum number of characters that can be read, which defines the length of the input text
-R	Mask Escape character
-P Prompt	Display the prompt information
-S	Silent mode, not displayed in the terminal when entering characters, often used for password input, etc.
-T Timeout	Specify the time-out period
-U FD	Read in from the file descriptor, the FD can be opened by exec

Usage examples

1. Read in from standard input

[[email protected] test]# cat read.sh#!/bin/bashecho -n "Please input your name:"read nameecho "Hello $name"[[email protected] test]# bash read.shPlease input your name:JackHello Jack

2, specify the display information from the standard input read into

[[email protected] test]# cat read.sh#!/bin/bash# echo -n "Please input your name:"read -p "Please input your name:" name# read nameecho "Hello $name"[[email protected] test]# bash read.shPlease input your name:JackHello Jack

In the example above, read can accept more than one parameter at a time, as follows:

read -p "Please input your name:" firstName secondName lastName

However, the following matters need to be noted:

• If the input data is less than the number of variables, the extra variable is not fetched to the data, that is, the variable value is empty
• If you enter more data than the number of variables, the excess data will all be assigned to the last variable
• If no variables are defined after the Read command, when the script executes, if the user enters data, the data is saved to the environment variable $REPLY

3. Specify the time-out period

[[email protected] test]# cat read.sh#!/bin/bashif read -t 3 -p "Please input your name:" firstName secondName lastNamethen  echo "variable is $firstName - $secondName - $lastName"else   echo -e  "\ntimeout\n"fi[[email protected] test]# bash read.shPlease input your name:timeout

4. Read content from the specified file

[[email protected] test]# cat-n test.txt 1 This is Test text.     2 this was second line. 3 Hello World 4 C # Main 5 python# using the-u option [[email protected] test]# cat readtest.sh#!/bin/bashexec 5< ~/t Est/test.txtcount=0while read-u 5 vardo let count= $count +1 echo "line $count are $var" Doneecho "Total line count is $count "Exec 5<&-[[email protected] test]# bash Readtest.shline 1 is this is Test text. Line 2 is the second line. Line 3 are Hello WorldLine 4 is C # MainLine 5 is Pythontotal lines count is AA use piping [[email protected] test]# cat Readte  St.sh#!/bin/bashcount=1cat ~/test/test.txt | While read Linedo echo ' current line $count-$line ' let count= $count +1doneecho ' total line count is $count ' [[email  Protected] test]# Bash Readtest.shcurrent line 1-this is Test text. Current line 2-this are second line. 3-hello worldcurrent line 4-c# maincurrent line 5-pythontotal line count is # Use REDIRECT [[Email protec Ted] test]# Cat Readtest.sh#!/bin/bashcount=0while Read Linedo let count= $count +1 Echo ' current line $count-$line ' Done < ~/test /test.txtecho "Total line count was $count" [[email protected] test]# bash readtest.shcurrent line 1-this is test Tex T.current line 2-this are second line. 3-hello worldcurrent line 4-c# maincurrent line 5-pythontotal line count is 5

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Linux Basic Tutorial 45-read command