Tell me more ×
Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems.. It's 100% free, no registration required.
up vote 29 down vote favorite
6

I am wondering if there is any historical or practical reason why the umount command is not unmount.

share|improve this question

2 Answers

up vote 32 down vote accepted

This dates all the way back to the very first edition of Unix, where all the standard file names were only at most 6 characters long (think passwd), even though this version supported a whooping 8 characters in a file name. Most commands had an associated source file ending in .c (e.g. umount.c), which left only 6 characters for the base name.

A 6-character limitation might also have been a holdover from an earlier development version, or inherited from a then-current IBM system that did have a 6-character limitation. (Early C implementations had a 6-character limit on identifiers — longer identifiers were accepted but the compiler only looked at the first 6 characters, so foobar1 and foobar2 were the same variable.)

(I thought I remembered a umount man page that listed the spelling as a bug of unknown origin, but I can't find it now.)

share|improve this answer
13  
6 character command name + .c (or .s) extension = 8 character filename limit. – geekosaur Mar 21 '11 at 21:25
@geekosaur: Ah, right, the source file. If you write an answer, I'll delete mine. – Gilles Mar 21 '11 at 21:37
2  
Enh, just annotate it if you want. – geekosaur Mar 21 '11 at 21:38
@geekosaur: I thought of the man page, as well, but V1 didn't have a man command (and one of the man pages is called directory, which wouldn't have fit yet). So I wonder why passwd was truncated to 6 characters (there wasn't a passwd command yet either, just /etc/passwd). – Gilles Mar 21 '11 at 22:52
Thank you! @geekosaur: +1 for your comment :) – uloBasEI Mar 23 '11 at 21:52
up vote 0 down vote

For the same reason the creat system call is not spelled create ?

http://stackoverflow.com/questions/1713457/what-did-ken-thompson-mean-when-he-said-id-spell-create-with-an-e

share|improve this answer
2  
Nope. The regret in the quote you reference is because they could have added the 'e' even in spite of the 6 character limit being argued over in the other answer. There really is no good reason for it to be truncated, unlike with umount. – Warren Young Mar 22 '11 at 2:50
I'm guessing by that time it was tradition to truncate letters if you could. – Shadur Mar 22 '11 at 8:00

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.