How to check if a file exists using Bash Shell-Python Tutorial-php.cn

How to check if a file exists using Bash Shell

高洛峰

Release： 2017-01-09 13:48:21

Original

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Preface

You may often encounter such needs when working. In the Bash environment of a Unix-like system, how to check whether a file exists? Since there is a need, of course there is a solution. The test command in the Shell can be used to detect the type of the file or compare whether the values are equal. This command can also be used to check whether the file exists.

You can use the following command to check:

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

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The following command uses Shell’s conditional expression to determine /etc/ Whether the hosts file exists:

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

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This combined command will output the following:

Found

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The more common usage is to place the test command in the conditional expression of if..else..fi conditional judgment, and then write different branch logic in it

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

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Related operators for detecting file attributes

If the file exists and has corresponding attributes, the following operators will return 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

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The above commands are copied from man test.

The method of using the above symbols is exactly the same:

if [ operator FileName ]
then
  echo "FileName - Found, take some action here"
else
 echo "FileName - Not found, take some action here"
fi

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##Summary

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