如何判断 Bash 中是否不存在常规文件？

How do I tell if a regular file does not exist in Bash?

提问by Bill the Lizard

I've used the following script to see if a file exists:

我使用以下脚本来查看文件是否存在：

#!/bin/bash

FILE=     
if [ -f $FILE ]; then
   echo "File $FILE exists."
else
   echo "File $FILE does not exist."
fi

What's the correct syntax to use if I only want to check if the file does notexist?

如果我只想检查文件是否不存在，那么使用的正确语法是什么？

#!/bin/bash

FILE=     
if [ $FILE does not exist ]; then
   echo "File $FILE does not exist."
fi

回答by John Feminella

The testcommand ([here) has a "not" logical operator which is the exclamation point (similar to many other languages). Try this:

该测试命令（[在这里）有一个“非”逻辑运算符是感叹号（类似于许多其他语言）。尝试这个：

if [ ! -f /tmp/foo.txt ]; then
    echo "File not found!"
fi

回答by BlueCacti

Bash File Testing

Bash 文件测试

-b filename- Block special file
-c filename- Special character file
-d directoryname- Check for directory Existence
-e filename- Check for file existence, regardless of type (node, directory, socket, etc.)
-f filename- Check for regular file existence not a directory
-G filename- Check if file exists and is owned by effective group ID
-G filename set-group-id- True if file exists and is set-group-id
-k filename- Sticky bit
-L filename- Symbolic link
-O filename- True if file exists and is owned by the effective user id
-r filename- Check if file is a readable
-S filename- Check if file is socket
-s filename- Check if file is nonzero size
-u filename- Check if file set-user-id bit is set
-w filename- Check if file is writable
-x filename- Check if file is executable

-b filename- 块特殊文件
-c filename- 特殊字符文件
-d directoryname- 检查目录是否存在
-e filename- 检查文件是否存在，无论类型如何（节点、目录、套接字等）
-f filename- 检查常规文件是否存在而不是目录
-G filename- 检查文件是否存在并归其所有有效组 ID
-G filename set-group-id- 如果文件存在并且设置为组 ID，则为真
-k filename- 粘滞位
-L filename- 符号链接
-O filename- 如果文件存在并由有效用户 ID 拥有，则为真
-r filename- 检查文件是否可读
-S filename- 检查文件是否为套接字
-s filename- 检查是否文件大小非零
-u filename- 检查文件设置用户 ID 位是否设置
-w filename- 检查文件是否可写
-x filename- 检查文件是否可执行

How to use:

如何使用：

#!/bin/bash
file=./file
if [ -e "$file" ]; then
    echo "File exists"
else 
    echo "File does not exist"
fi 

A test expressioncan be negated by using the !operator

甲测试表达可以通过使用被否定!操作者

#!/bin/bash
file=./file
if [ ! -e "$file" ]; then
    echo "File does not exist"
else 
    echo "File exists"
fi 

回答by BlueCacti

You can negate an expression with "!":

你可以用“！”否定一个表达式：

#!/bin/bash
FILE=

if [ ! -f "$FILE" ]
then
    echo "File $FILE does not exist"
fi

The relevant man page is man testor, equivalently, man [-- or help testor help [for the built-in bash command.

相关的手册页是man test或，等效地，man [-- 或help test或help [用于内置 bash 命令。

回答by guns

[[ -f $FILE ]] || printf '%s does not exist!\n' "$FILE"

Also, it's possible that the file is a broken symbolic link, or a non-regular file, like e.g. a socket, device or fifo. For example, to add a check for broken symlinks:

此外，该文件可能是损坏的符号链接或非常规文件，例如套接字、设备或 fifo。例如，要添加对损坏符号链接的检查：

if [[ ! -f $FILE ]]; then
    if [[ -L $FILE ]]; then
        printf '%s is a broken symlink!\n' "$FILE"
    else
        printf '%s does not exist!\n' "$FILE"
    fi
fi

回答by Elazar Leibovich

It's worth mentioning that if you need to execute a single command you can abbreviate

值得一提的是，如果你需要执行单个命令，你可以缩写

if [ ! -f "$file" ]; then
    echo "$file"
fi

to

到

test -f "$file" || echo "$file"

or

或者

[ -f "$file" ] || echo "$file"

回答by J. M. Becker

I prefer to do the following one-liner, in POSIXshell compatible format:

我更喜欢以POSIXshell 兼容格式执行以下单行操作：

$ [ -f "/$DIR/$FILE" ] || echo "$FILE NOT FOUND"

$ [ -f "/$DIR/$FILE" ] && echo "$FILE FOUND"

For a couple of commands, like I would do in a script:

对于几个命令，就像我在脚本中所做的那样：

$  [ -f "/$DIR/$FILE" ] || { echo "$FILE NOT FOUND" ; exit 1 ;}

Once I started doing this, I rarely use the fully typed syntax anymore!!

一旦我开始这样做，我就很少再使用完全类型化的语法了！！

回答by SD.

To test file existence, the parameter can be any one of the following:

要测试文件是否存在，该参数可以是以下任何一项：

-e: Returns true if file exists (regular file, directory, or symlink)
-f: Returns true if file exists and is a regular file
-d: Returns true if file exists and is a directory
-h: Returns true if file exists and is a symlink

All the tests below apply to regular files, directories, and symlinks:

下面的所有测试都适用于常规文件、目录和符号链接：

-r: Returns true if file exists and is readable
-w: Returns true if file exists and is writable
-x: Returns true if file exists and is executable
-s: Returns true if file exists and has a size > 0

Example script:

示例脚本：

#!/bin/bash
FILE=

if [ -f "$FILE" ]; then
   echo "File $FILE exists"
else
   echo "File $FILE does not exist"
fi

回答by Jahid

You can do this:

你可以这样做：

[[ ! -f "$FILE" ]] && echo "File doesn't exist"

or

或者

if [[ ! -f "$FILE" ]]; then
    echo "File doesn't exist"
fi

If you want to check for file and folder both, then use -eoption instead of -f. -ereturns true for regular files, directories, socket, character special files, block special files etc.

如果要同时检查文件和文件夹，请使用-eoption 而不是-f. -e对于常规文件、目录、套接字、字符特殊文件、块特殊文件等，返回 true。

回答by artdanil

You should be careful about running testfor an unquoted variable, because it might produce unexpected results:

运行test未加引号的变量时应该小心，因为它可能会产生意想不到的结果：

$ [ -f ]
$ echo $?
0
$ [ -f "" ]
$ echo $?
1

The recommendation is usually to have the tested variable surrounded by double quotation marks:

建议通常是将测试变量用双引号括起来：

#!/bin/sh
FILE=

if [ ! -f "$FILE" ]
then
   echo "File $FILE does not exist."
fi

回答by artdanil

There are three distinct ways to do this:

有三种不同的方法可以做到这一点：

1. Negate the exit status with bash (no other answer has said this):

   if ! [ -e "$file" ]; then
       echo "file does not exist"
   fi
   

   Or:

   ! [ -e "$file" ] && echo "file does not exist"
   

2. Negate the test inside the test command [(that is the way most answers before have presented):

   if [ ! -e "$file" ]; then
       echo "file does not exist"
   fi
   

   Or:

   [ ! -e "$file" ] && echo "file does not exist"
   

3. Act on the result of the test being negative (||instead of &&):

   Only:

   [ -e "$file" ] || echo "file does not exist"
   

   This looks silly (IMO), don't use it unless your code has to be portable to the Bourne shell (like the /bin/shof Solaris 10 or earlier) that lacked the pipeline negation operator (!):

   if [ -e "$file" ]; then
       :
   else
       echo "file does not exist"
   fi
   

1. 用 bash 否定退出状态（没有其他答案说过这个）：

   if ! [ -e "$file" ]; then
       echo "file does not exist"
   fi
   

   或者：

   ! [ -e "$file" ] && echo "file does not exist"
   

2. 否定测试命令中的测试[（这是之前大多数答案的呈现方式）：

   if [ ! -e "$file" ]; then
       echo "file does not exist"
   fi
   

   或者：

   [ ! -e "$file" ] && echo "file does not exist"
   

3. 根据测试结果是否定的（||而不是 ）采取行动&&：

   仅有的：

   [ -e "$file" ] || echo "file does not exist"
   

   这看起来很傻 (IMO)，除非您的代码必须可移植到/bin/sh缺少管道否定运算符 ( !)的 Bourne shell（如Solaris 10 或更早版本），否则不要使用它：

   if [ -e "$file" ]; then
       :
   else
       echo "file does not exist"
   fi