Done after a while loop in the shell followed by a redirect <

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How to read a file:

First step: Pass the contents of the file to the while by pipe (|) or redirect (<)

The second step is to call read in the while and read the contents of the file one line at a time and pay the value to the variable following read. The contents of the current row are saved in the variable.

For example, read file/sites/linuxpig.com.txt

1) How to pipe:

Cat/sites/linuxpig.com.txt |while Read Line
Do
Echo $LINE
Done

Of course, Cat/sites/linuxpig.com.txt can also be written in some complex, such as:

Example 1:
Find-type f-name "*.txt"-exec cat |while Read line
Do
Echo $LINE
Done
All files ending in. txt can be read in the current directory

Example 2:
Grep-r "linuxpig.com"./| Awk-f ":" ' {print $} ' | Cat |while Read Line
Do
Echo $LINE
Done

You can open and read all files that contain the string "linuxpig.com".

Examples are not actually tested, if used please test first ..... :-)

2) How to redirect:

2.1 Using redirects <

While Read line
Do
Echo $LINE
Done </sites/linuxpig.com.txt

2.2 Using file descriptors (0~9) and redirects <

EXEC 3<&0 #先将文件描述符0复制到文件描述符3, which is to make a backup of the file descriptor 0
EXEC 0</sites/linuxpig.com.txt #读文件到文件描述符0
While reading line # This variable is read data from stdin (that is, descriptor 0)
Do
Echo $LINE
Done
EXEC 0<&3 #将文件描述符3复制给文件描述符0 (recovery 0 read from keyboard)

Done after a while loop in the shell followed by a redirect <