Limit on File Name Length in Bash

Love The Way You Lie 2024-02-17 09:21 50阅读 0赞

### 1. Overview ###

In Unix-based systems, there is a limit on the length of filenames. This limit is different on different file systems.

In this tutorial, we’ll learn how to find the limit on different file systems. Additionally, we’ll create a file with a long name to confirm how the limit works.

### 2. File Name Length Limits and Unix File Systems ###

Most Unix file systems have similar filename length limits:

<table> 
 <tbody> 
  <tr> 
   <th>File System</th> 
   <th>Max File Name Length</th> 
  </tr> 
  <tr> 
   <td>BTRFS</td> 
   <td>255 bytes</td> 
  </tr> 
  <tr> 
   <td>exFAT</td> 
   <td>255 UTF-16 characters</td> 
  </tr> 
  <tr> 
   <td>ext2</td> 
   <td>255 bytes</td> 
  </tr> 
  <tr> 
   <td>ext3</td> 
   <td>255 bytes</td> 
  </tr> 
  <tr> 
   <td>ext3cow</td> 
   <td>255 bytes</td> 
  </tr> 
  <tr> 
   <td>ext4</td> 
   <td>255 bytes</td> 
  </tr> 
  <tr> 
   <td>FAT32</td> 
   <td>8.3 (255 UCS-2 code units with VFAT LFNs)</td> 
  </tr> 
  <tr> 
   <td>NTFS</td> 
   <td>255 characters</td> 
  </tr> 
 </tbody> 
</table>

However, since the Unicode representation of a character can occupy several bytes, the maximum number of characters that comprise a path and filename can vary.

Further, **the limits remain the same whether the filename contains an extension or not**. We can take a look at a more exhaustive [list][] of the filename and path limits depending on the file system.

We can also have extensions on our file system that change the maximum length limit. A good example of this is [eCryptFS][] which utilizes part of the lower filename to keep metadata and sets the limit of a filename to 143 characters.

### 3. Finding the Limit ###

Linux has a handy command called [getconf][] for querying system configuration variables.

We can run it to find the filename length limit:

$ getconf -a | grep -i name_max
    NAME_MAX                           255
    _POSIX_NAME_MAX                    255
    LOGNAME_MAX                        256
    TTY_NAME_MAX                       32
    TZNAME_MAX                         
    _POSIX_TZNAME_MAX                  
    CHARCLASS_NAME_MAX                 2048
    HOST_NAME_MAX                      64
    LOGIN_NAME_MAX                     256
    Copy

Here, the *NAME\_MAX* configuration represents the filename length limit.

Similarly, we can find the path length limit by modifying the last part of our previous command:

$ getconf -a | grep -i path_max
    PATH_MAX                           4096
    _POSIX_PATH_MAX                    4096Copy

### 4. Confirming the Limits ###

Let’s use the standard *[touch][]*command to try and create a file with a name containing 258 characters, i.e., three characters more than the limit of 255:

$ touch abcabcabcabcabcabcabc...other characters omitted....abcabcabc
    Copy

Here’s the response we get:

touch: cannot touch 'abcabcabcabcabcabcabc...other characters omitted....abcabcabc': File name too longCopy

### 5. Conclusion ###

In this article, we learned how to check both filename and path limits on different Linux file systems. We also tried to create a file that surpassed the limit to see the error we got.

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[list]: https://en.wikipedia.org/wiki/Comparison_of_file_systems
[eCryptFS]: https://bugs.launchpad.net/ecryptfs/+bug/344878
[getconf]: https://www.commandlinux.com/man-page/man1/getconf.1.html
[touch]: https://man7.org/linux/man-pages/man1/touch.1.html