前言
大家在工作的時候可能經常會遇到這樣的需求，在類Unix系統的Bash環境下，怎樣檢查文件是否存在呢？既然有需求，當然就有解決的辦法了，Shell中的test命令，可以用來檢測文件的類型或者比較數值是否相等，該命令也能用來檢查文件是否存在。
可以用如下的命令來進行檢查：
test -e filename
[ -e filename ]
test -f filename
[ -f filename ]
下面的命令，則使用Shell的條件表達式，判斷/etc/hosts文件是否存在：
[ -f /etc/hosts ] echo "Found" || echo "Not found"
該組合命令會輸出以下內容：
更常見的用法，則是將test命令放置在if..else..fi條件判斷的條件表達式，然后在其中寫上不同的分支邏輯
#!/bin/bash
file="/etc/hosts"
if [ -f "$file" ]
then
echo "$file found."
else
echo "$file not found."
fi
檢測文件屬性的相關操作符
如果文件存在，并且具有相應的屬性，如下的操作符都會返回true：
-b FILE
FILE exists and is block special
-c FILE
FILE exists and is character special
-d FILE
FILE exists and is a directory
-e FILE
FILE exists
-f FILE
FILE exists and is a regular file
-g FILE
FILE exists and is set-group-ID
-G FILE
FILE exists and is owned by the effective group ID
-h FILE
FILE exists and is a symbolic link (same as -L)
-k FILE
FILE exists and has its sticky bit set
-L FILE
FILE exists and is a symbolic link (same as -h)
-O FILE
FILE exists and is owned by the effective user ID
-p FILE
FILE exists and is a named pipe
-r FILE
FILE exists and read permission is granted
-s FILE
FILE exists and has a size greater than zero
-S FILE
FILE exists and is a socket
-t FD file descriptor FD is opened on a terminal
-u FILE
FILE exists and its set-user-ID bit is set
-w FILE
FILE exists and write permission is granted
-x FILE
FILE exists and execute (or search) permission is granted
以上命令，從man test復制而來。
使用上述符號的方法一模一樣：
if [ operator FileName ]
then
echo "FileName - Found, take some action here"
else
echo "FileName - Not found, take some action here"
fi
總結
以上就是這篇文章的全部內容了，希望本文的內容對大家的學習或者工作能帶來一定的幫助，如果有疑問大家可留言交流。
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