逐行读取文件并将值分配给变量 [英] Read a file line by line assigning the value to a variable

问题描述

我有以下 .txt 文件:

I have the following .txt file:

Marco
Paolo
Antonio

我想逐行读取它，对于每一行，我想将一个 .txt 行值分配给一个变量.假设我的变量是$name，流程是:

I want to read it line-by-line, and for each line I want to assign a .txt line value to a variable. Supposing my variable is $name, the flow is:

• 从文件中读取第一行
• 分配 $name = "Marco"
• 用$name
做一些任务
• 从文件中读取第二行
• 分配 $name = "Paolo"

• Read first line from file
• Assign $name = "Marco"
• Do some tasks with $name
• Read second line from file
• Assign $name = "Paolo"

推荐答案

以下内容逐行读取作为参数传递的文件:

The following reads a file passed as an argument line by line:

while IFS= read -r line; do
    echo "Text read from file: $line"
done < my_filename.txt

这是用于在循环中从文件中读取行的标准形式.说明:

This is the standard form for reading lines from a file in a loop. Explanation:

• IFS=(或 IFS='')可防止修剪前导/尾随空格.
• -r 防止反斜杠转义被解释.

• IFS= (or IFS='') prevents leading/trailing whitespace from being trimmed.
• -r prevents backslash escapes from being interpreted.

或者你可以把它放在一个bash文件帮助脚本中，示例内容:

Or you can put it in a bash file helper script, example contents:

#!/bin/bash
while IFS= read -r line; do
    echo "Text read from file: $line"
done < "$1"

如果以上保存为文件名为readfile的脚本，可以如下运行:

If the above is saved to a script with filename readfile, it can be run as follows:

chmod +x readfile
./readfile filename.txt

如果文件不是标准 POSIX 文本文件(= 不以换行符终止)，循环可以修改以处理尾随部分行:

If the file isn’t a standard POSIX text file (= not terminated by a newline character), the loop can be modified to handle trailing partial lines:

while IFS= read -r line || [[ -n "$line" ]]; do
    echo "Text read from file: $line"
done < "$1"

这里，<代码>||[[ -n $line ]] 防止最后一行不以 结尾(因为 read 返回非遇到 EOF 时退出代码为零).

Here, || [[ -n $line ]] prevents the last line from being ignored if it doesn't end with a (since read returns a non-zero exit code when it encounters EOF).

如果循环内的命令也从标准输入读取，则 read 使用的文件描述符可能会被替换为其他内容(避免使用 标准文件描述符)，例如:

If the commands inside the loop also read from standard input, the file descriptor used by read can be chanced to something else (avoid the standard file descriptors), e.g.:

while IFS= read -r -u3 line; do
    echo "Text read from file: $line"
done 3< "$1"

(非 Bash shell 可能不知道 read -u3；改用 read <&3.)

(Non-Bash shells might not know read -u3; use read <&3 instead.)

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