I have a general question as to why this occurs, and a misconception about 'pwd'.
You start with directory /test and in it you have /test/folder1.
Folder 1 has: file1.txt
In 2 separate terminals we "cd /test", and do an "ls" and discover folder1 as the output for both of these terminals.
We now "cd folder1" on terminal one. Terminal two remains in /test.
If we then "mv folder1 folder2" on terminal two and run an "ls" we get folder2 as the output. Clearly indicating our mv was successful.
However, within terminal 1 (which was in /test/folder1) if we run a "pwd" the output remains /test/folder1. Ie: it does NOT reflect that we have since moved the folder to /test/folder2.
Why is this the case? I can understand why if we were to edit the file1.txt it is just a pointer within the file system that should be pointing to the same file. Indeed it is as you can modify the file in each terminal and see the edits in the other. However, why is it the case that the 'pwd' command no longer reflects the actual path to that directory?
Thanks!
Assuming you're using bash, pwd is showing you the value of the PWD environment variable, which is updated when you change directory with cd. The folder1 directory changing name does not cause bash to update PWD. However you can find evidence that the directory has changed name:
pwd -P will show the new name of the directory.
ls -l /proc/self/cwd will link to the new name.
I think it is just the case that the first terminal has no reason to re-evaluate where it is. If you do the following command in the first terminal
cd .
you will see your current working directory has indeed changed per the rename (mv).
Related
How do I use winzip command line with include full path information ? I know I can do this under Winzip GUI but how to do it using cmd ? Also, is there a way to zip selected specific folders only ? Thanks
Tried GUI and it is working very slow
Winzip command line doesnt seem to zip selected folders - either parent folders or specific subfolders
I am using winzip 27 command line and this is the syntax I am using:
wzzip -a -e0 -k -P -r -yx "C:\Users\source\to\save\zipfile.zip" "C:\example"
This stores files and folder timestamps underneath C:\example. But since I have enabled -P -r, I want to store the timestamps of the upper folder, C:\example folder. How can I do that ? Does anyone have suggestions?
Also, how do I specify the path for a mapped network drive? Thanks!
I am running these three commands.
cd "${folder1}"
diff -ruN "${folder1}" "${folder2}" > "${patchname}"
patch -f -s -d "${folder1}" --merge < "${patchname}"
When I run them it successfully changes the files in folder1 to the same as folder2. However when I run these commands I get the output.
patch: **** Can't rename file ./update.patch.omMg8yG to update.patch : Operation not permitted
The problem is here:
cd "${folder1}"
diff -ruN "${folder1}" "${folder2}" > "${patchname}"
You're inside folder1, and trying to create a patch that's also inside folder1 (which we know because your log file is calling the file ./update.patch.omMg8yG, explicitly referring to the current directory), which contains a set of differences between folder1 and folder2, while those differences also include the contents of the output file itself -- the output file being generated over the course of the diff operation, and read over the course of patch operation.
Consequently, patch is trying to change the patch file it's reading from. It's failing, hence the error, but you shouldn't be having it make the attempt -- particularly since on most UNIXlike operating systems, this attempt wouldn't fail (I'm assuming you're on Cygwin, or on a remote filesystem mount that doesn't support open unlinked files).
Modify your patchfile variable to point to a location in a different directory, neither folder1 or folder2.
I'm attempting to open a directory in Unix. If I enter the command
ls
I see the directory listed in my current directory but if I endter
cd [directory_name]
I get the error
No such file or directory
I'm also not able to auto complete the directory name using the 'tab' key. Does anyone know what may be causing this?
Check whether you are using the right capitalization? It's case sensitive. Add this to your ~/.inputrc if you want bash to not care about the case of the file.
set completion-ignore-case on
This is example:
user#stackoverflow:~$ ls
users questions file.txt
user#stackoverflow:~$ cd /questions
user#stackoverflow:~/questions$
Make sure that you're trying to access a valid folder and not a file.
To further explain:
List the current directory's contents (either one):
ls .
ls
List the home directory's contents (wherever you are):
ls ~
List the root directory's contents (wherever you are):
ls /
So this doesn't seem like a terribly complicated question I have, but it's one I can't find the answer to. I'm confused about what the -p option does in Unix. I used it for a lab assignment while creating a subdirectory and then another subdirectory within that one. It looked like this:
mkdir -p cmps012m/lab1
This is in a private directory with normal rights (rlidwka). Oh, and would someone mind giving a little explanation of what rlidwka means? I'm not a total noob to Unix, but I'm not really familiar with what this means. Hopefully that's not too vague of a question.
The man pages is the best source of information you can find... and is at your fingertips: man mkdir yields this about -p switch:
-p, --parents
no error if existing, make parent directories as needed
Use case example: Assume I want to create directories hello/goodbye but none exist:
$mkdir hello/goodbye
mkdir:cannot create directory 'hello/goodbye': No such file or directory
$mkdir -p hello/goodbye
$
-p created both, hello and goodbye
This means that the command will create all the directories necessaries to fulfill your request, not returning any error in case that directory exists.
About rlidwka, Google has a very good memory for acronyms :). My search returned this for example: http://www.cs.cmu.edu/~help/afs/afs_acls.html
Directory permissions
l (lookup)
Allows one to list the contents of a directory. It does not allow the reading of files.
i (insert)
Allows one to create new files in a directory or copy new files to a directory.
d (delete)
Allows one to remove files and sub-directories from a directory.
a (administer)
Allows one to change a directory's ACL. The owner of a directory can always change the ACL of a directory that s/he owns, along with the ACLs of any subdirectories in that directory.
File permissions
r (read)
Allows one to read the contents of file in the directory.
w (write)
Allows one to modify the contents of files in a directory and use chmod on them.
k (lock)
Allows programs to lock files in a directory.
Hence rlidwka means: All permissions on.
It's worth mentioning, as #KeithThompson pointed out in the comments, that not all Unix systems support ACL. So probably the rlidwka concept doesn't apply here.
-p|--parent will be used if you are trying to create a directory with top-down approach. That will create the parent directory then child and so on iff none exists.
-p, --parents
no error if existing, make parent directories as needed
About rlidwka it means giving full or administrative access. Found it here https://itservices.stanford.edu/service/afs/intro/permissions/unix.
mkdir [-switch] foldername
-p is a switch, which is optional. It will create a subfolder and a parent folder as well, even if parent folder doesn't exist.
From the man page:
-p, --parents no error if existing, make parent directories as needed
Example:
mkdir -p storage/framework/{sessions,views,cache}
This will create subfolder sessions,views,cache inside framework folder irrespective of whether 'framework' was available earlier or not.
PATH: Answered long ago, however, it maybe more helpful to think of -p as "Path" (easier to remember), as in this causes mkdir to create every part of the path that isn't already there.
mkdir -p /usr/bin/comm/diff/er/fence
if /usr/bin/comm already exists, it acts like:
mkdir /usr/bin/comm/diff
mkdir /usr/bin/comm/diff/er
mkdir /usr/bin/comm/diff/er/fence
As you can see, it saves you a bit of typing, and thinking, since you don't have to figure out what's already there and what isn't.
Note that -p is an argument to the mkdir command specifically, not the whole of Unix. Every command can have whatever arguments it needs.
In this case it means "parents", meaning mkdir will create a directory and any parents that don't already exist.
I have shell script which starts with:
sdir=`dirname $0`
sdir=`(cd "$sdir/"; pwd)`
And this usually gets expanded (with 'sh -h') into
++ dirname /opt/foo/bin/bar
+ sdir=/opt/foo/bin
++ cd /opt/foo/bin/
++ pwd
+ sdir=/opt/foo/bin
but for single user for single combination of parameters in expands into (note two lines at the result sbin value)
++ dirname bin/foo
+ sdir=bin
++ cd bin/
++ pwd
+ sdir='/opt/foo/bin
/opt/foo/bin'
I tried different combinations but was not able to reproduce this behavior. With different input parameters for that user it started producing correct single line result. I am new to shell scripting, so please advice when such (cd X; pwd) can return two line.
it was observed on CentOS, but not sure it that matters. Please advice.
The culprit is cd, try this instead
sdir=`dirname $0`
sdir=`(cd "$sdir/" >/dev/null; pwd)`
This happens because when you specify a non absolute path and the directory is found in the environment variable CDPATH, cd prints to stdout the value of the absolute path to the directory it changed to.
Relevant man bash sections:
CDPATH The search path for the cd command. This is a
colon-separated list of directories in which the
shell looks for destination directories specified
by the cd command. A sample value is ``.:~:/usr''.
cd [-L|-P] [directory]
Change the current working directory to directory. If
directory is not given, the value of the HOME shell
variable is used. If the shell variable CDPATH exists,
it is used as a search path. If directory begins with a slash,
CDPATH is not used.
The -P option means to not follow symbolic links; symbolic
links are followed by default or with the -L option. If
directory is ‘-’, it is equivalent to $OLDPWD.
If a non-empty directory name from CDPATH is used, or if ‘-’
RELEVANT -\ is the first argument, and the directory change is successful,
PARAGRAPH -/ the absolute pathname of the new working directory is written
to the standard output.
The return status is zero if the directory is successfully
changed, non-zero otherwise.
OLDPWD The previous working directory as set by the cd
command.
CDPATH is a common gotcha. You can also use "unset CDPATH; export CDPATH" to avoid the problem in your script.
It's possible that user has some funky alias for "cd". Perhaps you could try making it do "/usr/bin/cd" (or whatever "cd" actually runs by default) instead.
Some people alias pwd to "echo $PWD". Also, the pwd command itself can either be a shell built-in or a program in /usr/bin. Do an "alias pwd" and "which pwd" on both that user and any user that works normally.
Try this:
sdir=$( cd $(dirname "$0") > /dev/null && pwd )
It's just a single line and will keep all special characters in the directory name intact. Remember that on Unix, only two characters are illegal in a file/dir name: 0-byte and / (forward slash). Especially, newlines are valid in a file name!