What does . (dot) mean as the destination of the cp command?
For example:
cp ~dir1/dir2/dir3/executableFile.x .
When this executes it copies the file successfully with the correct file name, but I'm wondering is this what a destination of '.' will always do or is there another purpose?
Within the reference material I've seen, dots are used in front of files to indicate 'hidden', but in that has no relation to the command above.
dot represents the current directory
while dotdot is the parent directory.
As EvilTeach's answer says, . is the current directory, and .. is the parent directory.
There are basically two ways to use the cp command:
cp file1 file2
will copy file1 to file2, creating file2 if it doesn't exist or (depending on permissions) possibly clobbering it if it does.
The other way is:
cp file1 file2 ... dir
where dir is an existing directory. With this form, you can specify one or more files, and they'll all be copied into the specified directory dir with their existing names.
(This can be a pitfall sometimes; cp foo bar behaves very differently depending on whether there's an existing directory named bar.)
As you mention, files (including directories) whose names start with . are hidden. What this means is that (a) the ls command won't list them (unless you use the -a or -A option), and (b) a shell wildcard such as * or *.txt will omit them. (GUI directory managers such as Nautilus may also omit them, depending on your settings.)
This applies to the current directory . and the parent directory ... ls won't include the . and .. entries in its output; ls -a will.
Related
I have two directories:
Directory #1, 'C'
C's absolute path:
/A/B/C
Directory #2, 'T'
T's absolute path:
/Q/R/T
I want to use rsync, to copy all files, recursively, from C, and copy them in to T, while maintaining the original directory structure - but only from B onwards.
Example to make it clearer: suppose 'B' has only 3 files nested within it:
/A/B/f1.txt
/A/B/C/f2.txt
/A/B/C/D/f3.txt
Then I want to end up with only f2.txt and f3.txt being copied over, with the final filepaths as follows (notice how I keep the directory structure, only from B onwards):
/Q/R/T/B/C/f2.txt
/Q/R/T/B/C/D/f3.txt
Here is the catch: I must execute the rsync cmd from within /Q/R/. So when I execute this command, my pwd must be /Q/R/.
Can anyone help me figure out how to do this?
[If I did not have this constraint of where my cwd must be, I could cd to /A/B, and then execute: rsync . /Q/R/T/ --recursive --relative . Unfortunately, I can not do that for reasons that would take a lot of pointless explaining here. And when I try to execute rsync /A/. /Q/R/T/ --recursive --relative, I end up with not only everything within A, but maintaining that first part of the dir structure (/A/) that I don't want. (Note - in the real life scenario the dir structure is much more complex then this, this is just the general problem.]
The rsync command includes a couple of options which are suitable for this scenario. They are:
--include=PATTERN - Don't exclude files matching PATTERN
--exclude=PATTERN - Exclude files matching PATTERN
An excellent description and examples of the --exclude flag can be found here.
Solution
Given the directory structures provided in your question and your pwd being set to /Q/R/. Running the following command will meet your requirement:
rsync ../../A/ T/ --recursive --include A/B/** --exclude B/*.*
Edit:
If you do want /A/B/f1.txt to copy to /Q/R/T/B/f1.txt (as it's unclear in your question because you don't show it in the "I want to end up with" example"). Then omit the --exclude B/*.* part, so the complete command is reduced to:
rsync ../../A/ T/ --recursive --include A/B/**
or reduced even further in complexity to just:
rsync ../../A/** T/ --recursive
Explanation of the command
../../A/
The first argument provides the path to the source directory. I.e. The relative position within the hierarchical tree of names (Based on your pwd being /Q/R).
T/
The second argument provides the path to the destination directory. Again this is a relative position within the hierarchical tree of names (and is also based on the pwd being /Q/R).
--recursive
The first option is to recurse into the directories.
--include A/B/**
This says that you want to include all the assets (files/folders), however many levels deep, from within the folder named B which resides inside folder A.
--exclude B/*.*
This says that you want to exclude any assets (files/folders), whose name includes a dot [.] plus extension, which reside inside folder B (at the top level). This will prevent the file named f1.txt from being copied. You could be even more specific here and use --exclude B/f1.txt instead, however I'm assuming in real life you perhaps have additional files you want to exclude here too.
Additional notes
Both the --include and --exclude options can be utilized multiple times. This can be very useful for some scenarios too as it enables you to be specific about what to include and/or exclude during the copy process.
For example, lets assume that your source directory /A/B/, (as described in your question), also contains a folder named X. So its path is A/B/X.
Lets say that we also do not want to copy this folder named X (in the same way as you currently do not want to copy /A/B/f1.txt).
For this scenario we add another --exclude option as follows:
rsync ../../A/ T/ --recursive --include A/B/** --exclude B/*.* --exclude X/
Note the additional --exclude X/ at the end.
You mention...
(Note - in the real life scenario the dir structure is much more complex then this, this is just the general problem.
... in your question, so you may find it necessary to add additional --exclude=PATTERN to truly meet your requirements.
Grunt
As you have included the gruntjs flag with your question, then you may want to consider utilizing plug-ins which can run shell commands like rsync such as:
grunt-shell
grunt-exec
Using Make is there a nice way to depend on a directories contents.
Essentially I have some generated code which the application code depends on. The generated code only needs to change if the contents of a directory changes, not necessarily if the files within change their content. So if a file is removed or added or renamed I need the rule to run.
My first thought is generate a text file listing of the directory and diff that with the last listing. A change means rerun the build. I think I will have to pass off the generate and diff part to a bash script.
I am hoping somehow in their infinite intelligence might have an easier solution.
Kudos to gjulianm who got me on the right track. His solution works perfect for a single directory.
To get it working recursively I did the following.
ASSET_DIRS = $(shell find ../../assets/ -type d)
ASSET_FILES = $(shell find ../../assets/ -type f -name '*')
codegen: ../../assets/ $(ASSET_DIRS) $(ASSET_FILES)
generate-my-code
It appears now any changes to the directory or files (add, delete, rename, modify) will cause this rule to run. There is likely some issue with file names here (spaces might cause issues).
Let's say your directory is called dir, then this makefile will do what you want:
FILES = $(wildcard dir/*)
codegen: dir # Add $(FILES) here if you want the rule to run on file changes too.
generate-my-code
As the comment says, you can also add the FILES variable if you want the code to depend on file contents too.
A disadvantage of having the rule depend on a directory is that any change to that directory will cause the rule to be out-of-date — including creating generated files in that directory. So unless you segregate source and target files into different directories, the rule will trigger on every make.
Here is an alternative approach that allows you to specify a subset of files for which additions, deletions, and changes are relevant. Suppose for example that only *.foo files are relevant.
# replace indentation with tabs if copy-pasting
.PHONY: codegen
codegen:
find . -name '*.foo' |sort >.filelist.new
diff .filelist.current .filelist.new || cp -f .filelist.new .filelist.current
rm -f .filelist.new
$(MAKE) generate
generate: .filelist.current $(shell cat .filelist.current)
generate-my-code
.PHONY: clean
clean:
rm -f .filelist.*
The second line in the codegen rule ensures that .filelist.current is only modified when the list of relevant files changes, avoiding false-positive triggering of the generate rule.
If I have a directory tree that looks like this:
parent/
child/
many files
What command/commands should I use to quickly make it like this:
parent/
many files
Effectively, I just want to remove one level of folder nesting. I don't care about any other files currently in parent.
This is what you do:
cd parent
mv child/* .
rmdir child
If you have files beginning with . (dot) in the child/ directory, you have to do
shopt -s dotglob
in order for the * to match them (there are other ways to force this, but setting dotglob is the easiest).
If child/ contains a file or directory named child, then you have to either rename that or the directory parent/child before the mv operation.
What about this?
mkdir new
find parent -type f -exec mv {} new/. \;
That would work for any depth of directory.
Trying to rename a set of files in a directory with various filetypes, all with one common word, say 'foo', to another word, say 'bar' on a MacBook Pro.
E.g.:
foo.txt
form_foo.plist
home_foo.png
images_foo.zip
->
bar.txt
form_bar.plist
home_bar.png
images_bar.zip
Any ideas?
Use with care:
ls | grep foo | while read -r name; do echo mv "$name" "${name//foo/bar}"; done
That will report the commands it will run when you omit "echo". Inspect
the results, then rerun with "echo" omitted. This makes no attempt to work
on files with newlines in the name, nor does it recurse into subdirectories. If you want to work with files whose name begins with ., add -a to the invocation of ls. For safety's sake, you may want to add -i to the invocation of mv. Certainly make a backup first.
I don't have access to a Mac, but under Ubuntu you can use the rename command for this. Here's the man page in case that command is available
I did some havoc on my computer, when I played with the commands suggested by vezult [1]. I expected the one-liner to ask file-names to be removed. However, it immediately removed my files in a folder:
> find ./ -type f | while read x; do rm "$x"; done
I expected it to wait for my typing of stdin:s [2]. I cannot understand its action. How does the read command work, and where do you use it?
What happened there is that read reads from stdin. When you put it at the end of a pipe, it read from that pipe.
So your find becomes
file1
file2
and so on; read reads that and replaces x successively with file1 then file2, and so your loop becomes
rm "file1"
rm "file2"
and sure enough, that rm's every file starting at the current directory ".".
A couple hints.
You didn't need the "/".
It's better and safer to say
find . -type f
because should you happen to type ". /" (ie, dot SPACE slash) find will start at the current directory and then go look starting at the root directory. That trick, given the right privileges, would delete every file in the computer. "." is already the name of a directory; you don't need to add the slash.
The find or rm commands will do this
It sounds like what you wanted to do was go through all the files in all the directories starting at the current directory ".", and have it ASK if you want to delete it. You could do that with
find . -type f -exec rm -i {} \;
or
find . -type f -ok rm {} \;
and not need a loop at all. You can also do
rm -r -i *
and get nearly the same effect, except that it will try to delete directories too. If the directory is empty, that'll even work.
Another thought
Come to think of it, unless you have a LOT of files, you could also do
rm -i `find . -type f`
Now the find in backquotes will become a bunch of file names on the command line, and the '-i' interactive flag on rm will ask the yes or no question.
Charlie Martin gives you a good dissection and explanation of what went wrong with your specific example, but doesn't address the general question of:
When should you use the read command?
The answer to that is - when you want to read successive lines from some file (quite possibly the standard output of some previous sequence of commands in a pipeline), possibly splitting the lines into several separate variables. The splitting is done using the current value of '$IFS', which normally means on blanks and tabs (newlines don't count in this context; they separate lines). If there are multiple variables in the read command, then the first word goes into the first variable, the second into the second, ..., and the residue of the line into the last variable. If there's only one variable, the whole line goes into that variable.
There are many uses. This is one of the simpler scripts I have that uses the split option:
#!/bin/ksh
#
# #(#)$Id: mkdbs.sh,v 1.4 2008/10/12 02:41:42 jleffler Exp $
#
# Create basic set of databases
MKDUAL=$HOME/bin/mkdual.sql
ELEMENTS=$HOME/src/sqltools/SQL/elements.sql
cat <<! |
mode_ansi with log mode ansi
logged with buffered log
unlogged
stores with buffered log
!
while read dbs logging
do
if [ "$dbs" = "unlogged" ]
then bw=""; cw=""
else bw="-ebegin"; cw="-ecommit"
fi
sqlcmd -xe "create database $dbs $logging" \
$bw -e "grant resource to public" -f $MKDUAL -f $ELEMENTS $cw
done
The cat command with a here-document has its output sent to a pipe, so the output goes into the while read dbs logging loop. The first word goes into $dbs and is the name of the (Informix) database I want to create. The remainder of the line is placed into $logging. The body of the loop deals with unlogged databases (where begin and commit do not work), then run a program sqlcmd (completely separate from the Microsoft new-comer of the same name; it's been around since about 1990) to create a database and populate it with some standard tables and data - a simulation of the Oracle 'dual' table, and a set of tables related to the 'table of elements'.
Other scripts that use the read command are bigger (by far), but generally read lines containing one or more file names and some other attributes of relevance, and then apply an appropriate transform to the files using the attributes.
Osiris JL: file * | grep 'sh.*script' | sed 's/:.*//' | xargs wgrep read
esqlcver:read version letter
jlss: while read directory
jlss: read x || exit
jlss: read x || exit
jlss: while read file type link owner group perms
jlss: read x || exit
jlss: while read file type link owner group perms
kb: while read size name
mkbod: while read directory
mkbod:while read dist comp
mkdbs:while read dbs logging
mkmsd:while read msdfile master
mknmd:while read gfile sfile version notes
publictimestamp:while read name type title
publictimestamp:while read name type title
Osiris JL:
'Osiris JL: ' is my command line prompt; I ran this in my 'bin' directory. 'wgrep' is a variant of grep that only matches entire words (to avoid words like 'already'). This gives some indication of how I've used it.
The 'read x || exit' lines are for an interactive script that reads a response from standard input, but exits if the command gets EOF (for example, if standard input comes from /dev/null).