The echo command of linux is very commonly used in shell programming. It is also often used when printing variable values under the terminal. Therefore, it is necessary to understand the usage of
echo. The function of the echo command is to display a piece of text on the display, which generally acts as a The role of prompting.
The general format of this command is: echo [ -n ] string
The option n means that the output text will not be newline; the string can be quoted or not. When using the echo command to output a quoted string, the string is output as it is; when using the echo command to output an unquoted string, each word in the string is output as a string, and each string is separated by a space .
Function description: Display text.
Syntax: echo [-ne][string] or echo [--help][--version]
Additional description: echo will send the input string to standard output. The output strings are separated by whitespace characters and appended with a newline at the end.
Parameters: -n Don't wrap the line at the end
-e If the following characters appear in the string, treat them specially instead of treating them as normal
- # echo [Options] [String]
Items in square brackets are optional. A string can be defined as a finite sequence of characters (such as letters, numbers, symbols, punctuation).
When the echo command is used without any options or strings, it returns a blank line on the display followed by a new line to follow the command prompt. This is because pressing the enter key sends a signal to the system to start a new line, and echo repeats that signal.
Options:
- -n do not output derived newlines
- -e enable backslash escape interpretation
- -E disable backslash escape interpretation (default)
If you use the -e option, you can use escape sequences like this:
- \ backslash
- \a Warning (BEL)
- \b backslash
- \c produces no further output
- \e escape
- \f form feed
- \n new line
- \r newline character
- \t horizontal tab
- \v vertical tab
- \0NNN Octal value representation of byte NNN (1 to 3 digits)
- \xHH Byte NNN (1 to 2 digits) represented by hexadecimal value
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2.显示转义字符
echo "\"It is a test\"" 结果将是: "It is a test" 同样，双引号也可以省略
3.显示变量
read 命令从标准输入中读取一行,并把输入行的每个字段的值指定给 shell 变量 #!/bin/sh read name echo "$name It is a test"
以上代码保存为 test.sh，name 接收标准输入的变量，结果将是: [root@www ~]# sh test.sh OK #标准输入 OK It is a test #输出
4.显示换行
echo -e "OK! \n" # -e 开启转义 echo "It it a test"
输出结果： OK! It it a test
5.显示不换行
#!/bin/sh echo -e "OK! \c" # -e 开启转义 \c 不换行 echo "It is a test" 输出结果：OK! It is a test
- 转义
\a 发出警告声；
\b 删除前一个字符；
\c 最后不加上换行符号；
\f 换行但光标仍旧停留在原来的位置；
\n 换行且光标移至行首；
\r 光标移至行首，但不换行；
\t 插入tab；
\v 与\f相同；
\\ 插入\字符；
\nnn 插入nnn（八进制）所代表的ASCII字符；
6.显示结果定向至文件
echo "It is a test" > myfile
7.原样输出字符串，不进行转义或取变量(用单引号)
echo '$name\"' 输出结果： $name\"
8.显示命令执行结果
echo `date` 结果将显示当前日期 Thu Jul 24 10:08:46 CST 201