On 10/13/2011 02:45 AM, Morty wrote: > [This is more of a feature request than a bug request. But I don't > see where I can make feature requests.] > > It would be nice if touch had an option to only "touch" if the file > doesn't already exist. Sort of like -c, but the other way around. > This is useful because often, the reason one is using "touch" in a > script is because one wants to make sure that a file exists before > doing an operation that expects the file to already exist. But if the > file already exists, then touch has a side effect of changing the > mtime or the atime. [On many systems, one can work on a file without > changing the atime thanks to mount options such as noatime or > relatime.] > > It's easy enough to wrap touch in an if: > > if [ ! -e $file ]; then touch $file; fi > > But it would be nicer if this common case were built in. I would > suggest -e, for exists. Thanks!
Note the above is easier to express in shell like: [ -e "$file" ] || touch "$file" But that is racy. If you were using touch for locking purposes then adding -e (must create), would allow one to add O_EXCL to the open(), so you could then do things like: until touch -e "$lock_file"; do sleep .1; done However that functionality is already supported like: until mkdir "$lock_dir"; do sleep .1; done So I'm not sure this is warranted. I'm 60:40 against currently. cheers, Pádraig.
