使用Bash Shell檢查檔案是否存在的方法

前言

大家在工作的時候可能常常會遇到這樣的需求，在類Unix系統的Bash環境下，怎麼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指令，可以用來偵測檔案的類型或比較數值是否相等，該指令也能用來檢查檔案是否存在。

可以用以下的指令來檢查：

test -e filename
[ -e filename ]
  
test -f filename
[ -f filename ]

   

下面的指令，則使用Shell的條件式，判斷/etc/hosts輸出以下內容：

[ -f /etc/hosts ] && echo "Found" || echo "Not found"

   

較常見的用法，則是將test指令放置在if..else..fi條件判斷的條件表達式，然後在其中寫上不同的分支邏輯

Found

 

偵測檔案屬性的相關運算子

如果檔案存在，且有對應的屬性，下列的運算子都會回傳true：

#!/bin/bash
file="/etc/hosts"
if [ -f "$file" ]
then
 echo "$file found."
else
 echo "$file not found."
fi

   

以上指令，從man test複製而來。

使用上述符號的方法一模一樣：

-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

   

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，如果有疑問可留言交流。

更多使用Bash Shell檢查檔案是否存在的方法相關文章請關注PHP中文網！