Files – Understanding Filename and Pathname of a File

filenamesfiles

It is said that the filename of a file is a pointer pointing to the inode of the file.
Before knowing that, I thought it was the pathname of a file that does that job.

I am not sure how a pathname and a filename are defined in Unix.
For example, is it correct that
/home/tim/tim.pdf is the pathname of the file with file name tim.pdf.

I wonder what the difference between the filename and the pathname of a file? Thanks.

Best Answer

In POSIX terminology, a filename is the name of a directory entry. It consists of a non-empty sequence of bytes other than / or null. The term “pathname component” is synonymous with “filename”. A pathname is a string that can contain any non-null byte and that designates a way to locate a file. A pathname consists of a series of filenames, in which all but the last refer to a directory. Pathname resolution is the process of locating a file from a pathname.

For example, /home/tim/tim.pdf is a pathname. The last component of that pathname tim.pdf is a filename; it is the name of an entry in the directory whose pathname is /home/tim. The filename tim is itself the name of an entry in the directory whose pathname is /home; this file happens to be a directory. tim.pdf is also a pathname: any filename is a pathname that happens to have a single component and designates the file with that name in the current directory.

/ is a pathname that refers to the root directory. . is a filename that exists in every directory and refers to that directory itself. . is a pathname which happens to contain a single component and refers to the current directory.

You can think of a filename as a pointer within a directory to an inode that is a file in that directory. A pathname is a specification of where to find an inode. Each component of a pathname is a filename that points to an inode in the directory reached so far (if the file exists). Pathnames either start at the root directory (if they are absolute pathnames, beginning with /) or at the current directory (if they are relative pathnames, not beginning with /).

Note that in many texts, the word “filename” (or “file name”) is used to mean what POSIX calls a pathname.

Related Solutions

Bash shell script to locate and remove substring within a filename

Try this:

newname=`echo "$filename" | sed -e 's/\(S[0-9][0-9]E[0-9][0-9]\).*\.mp4/\1.mp4/'`

The regular expression is:

start a group ( \( )
match SXXEXX where X is a numeral between 0 and 9
end group ( \) )
match any number of any character (except a newline)
match a explicit string ( .mp4 )

In the replacement expression:

replace with string matched in first group ( \1 )
replace with explicit string ( .mp4 )

Is space not allowed in a filename

Spaces, and indeed every character except / and NUL, are allowed in filenames. The recommendation to not use spaces in filenames comes from the danger that they might be misinterpreted by software that poorly supports them. Arguably, such software is buggy. But also arguably, programming languages like shell scripting make it all too easy to write software that breaks when presented with filenames with spaces in them, and these bugs tend to slip through because shell scripts are not often tested by their developers using filenames with spaces in them.

Spaces replaced with %20 is not often seen in filenames. That's mostly used for (web) URLs. Though it's true that %-encoding from URLs sometimes makes its way into filenames, often by accident.

Best Answer

Related Solutions

Bash shell script to locate and remove substring within a filename

Is space not allowed in a filename

Related Question