What's the reason behind having -n option for mv command?
Sorry for a question that may seem dumb but learning UNIX basics I still can not grasp benefits of using
I can understand the need for
when you get a copy with contents untouched but the former baffles me.
I know that this about preventing from overwriting a target file with contents of a source file (not in opposite order, right?) but why rename at all if you don't want to annihilate the target file? What's the point?
Would be glad to feel enlightened on the subject.
Last edited by scrutinizerix; 02-29-2016 at 02:03 PM..
I still can not grasp benefits of using
What's the point?
According to the man page of OS X i found in the net "-n" prevents the mv command to overwrite already existing files. That means: if you have files A, B and C and you do a
you will end up with three files again, B, C and D (the former A). Whereas, when you issue:
you will end up with only two files: B (the former A) and C. The original B will be wiped out. This may sometimes be the desired result, but sometimes it may not. To guard against accidentally wiping out a file you might want to keep is the reason "-n" exists.
Both A and B are untouched so B IS NOT the former A. Right?
Yes. This is what i'd expect.
I'd also expect some diagnostic message to be issued (i don't have OS X but i suppose it would be something along the lines of "Error: cannot ....") and the return-code to be non-zero. This is a common trait of UNIX-commands: whenenver they cannot do what is asked they will return a non-zero error code. Try the following:
/etc/hosts is a file supposed to exist, so the return code should be zero, the second file does not exist, so the error code will be presumably 2 (if OS X-ls works the same way as my ls on AIX, the value might differ but it should be non-zero in any case).
Below are the screenshots of my actions in OS X Terminal. As you see there're no alert messages. I have cat'ed both files beforehand so that their contents became evident. If I pass -n option then nothing happens - both are kept in the state they used to prior running the command (as evidenced in the portion of their directory listing I invoked through ls -lahG command).
Hi folks,
I totally dislike asking questions in forums but this one eats up to much of my time I need to spend on other topics.
I have a shell-script in which I call a terminal.
I want to invoke bash inside the terminal and print a message inside bash with aid of a here document.
See... (7 Replies)
Dear all,
I want to execute fsck command,can i execute fsck command without any option
asking for more confidence.
Thanks and Regards
Monoj Das (1 Reply)
I am just learning shell scripting and already I found out I have the bad habit of thinking that it is similar to php or c.
I learned some basics and now encountered this problem:
On shell it is possible to type:
$ date --date="2009-10-10 09:08:34"
Sat Oct 10 09:08:34 CEST 2009
... (2 Replies)
Hi Friends,
I could see following oracle process in the glance command. i see nothing running in the database although. I tried google it but no success. Another team ,which needs all the processes on the server is complaining. Can someone help me what exactly are these sessions/ how to ... (1 Reply)
Hi,
what is the meaning of -n option before the grep command ?
grep command searches for the specified string in the file tmp_crontab.txt
but what does -n mean ?
With Regards (1 Reply)
Running HP 11.31 on a HP3600. But when I log in as a user the who command works but if I use an option like "who -m" I get nothing. Any thoughts on what is causing this problem. (11 Replies)
How can I use the 'ps' command to view current sessions but only for a given process/user, with the -u parm?
In older versions of Unix, this used to work, but not in Sun Solaris.
Thanks (4 Replies)
i'm using SunOS 5.7 and I know theres a ls option for seeing what kind of files are in a directory. I was wondering if there was a ls option that could see if the files are txt or files that can be opened in vi (1 Reply)