How long can file names be?

Question

How long can be files names and folder names in Ubuntu Linux and what characters are allowed in file name and folder name in Ubuntu Linux?

Answer 1

File names in Linux were 14 bytes long in earlier Unix version. But The modern Linux system has 255 bytes for file names.

As a character requires 1 byte, The length becomes 255 characters. Also the folders are treated as files in Linux system

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Answer 2

I'm not sure what the maximum file name length can be (for ext4), but it's more dependent on the file system, than Linux itself. On FAT32, I think it is 255 characters. You probably don't ever actually need a file name that long.

As for characters allowed, any byte value is allowed on the ext4 file system, except for the NULL byte (and /, as that is the directory separator¹). However, you should limit your file names to the UTF-8 character set, for the widest range of compatibility across applications, and devices.

^{1. As stated in the glibc manual, "any character except the null character is permitted in a file name string," but a / in the file name string separates the name of one file or folder from that of its parent.}