build.sh contains such code in the beginning:
. ./build.include
I am new to shell and don't know what this means.
I know that . stands for current directory.
and in the same directory of build.sh there is a file named build.include
But what does it mean if . and ./build.include appears in the same row?
There is a file called build.include in the current directory that will be read in and executed in that point in the script.
In this case, build.include contains a bunch of library functions used by build.sh.
Related
Ok so i did something very stupid (copying a file and renaming it '.') since I thought it would just copy it as .uniprot_sprot.fasta.gz.icloud.
cp /path/.uniprot_sprot.fasta.gz.icloud .
and now I don't know how to remove it from current directory as it would be removing '.' itself.
What can I do?
This doesn't work. It says: No such file or directory
rm .uniprot_sprot.fasta.gz.icloud
On the other hand:
ls -a
gives this:
.
..
uniprot_sprot.fasta.gz.icloud
You have not copied a file and renamed it . (at any rate if you're running a sane *nix). Instead you have copied the file to the current directory with the name of the original file. (If you pass a directory to cp as the destination, files will be placed in that directory. . is the current directory, so this is all that has happened.) If you want to remove it you can just rm uniprot_sprot.fasta.gx.iscloud or explicitly rm ./uniprot_sprot.fasta.gx.iscloud. What you have tried to do is to remove a file whose name starts with ., which is a different thing.
Edit: I was unaware when I wrote this, but this is in fact simply down to . existing as a real, regular hardlink. At syscall level you can create a file whose name contains anything except / and \x00 (yep, including \n), assuming your filesystem allows it. However, the links . and .. are already present and thus unavailable as a file name. #thatotherguy links to the kernel source for the rmdir syscall, showing that in modern Linux at least it is the kernel itself which ultimately prevents you from deleting . and ...
Note that in bash, . at the beginning of a line by itself means source.
See this question on unix.se and its linked dupe for more information on the filename problem.
How do . and .., as paths (vs. ranges, e.g., {1..10}, which I'm not concerned with), really work? I know what they do, and use them all the time, but don't fully grasp how/where they're interpreted. Does the shell handle them? The interpreting process? The OS?
The reason why I'm asking is that I'd like to be able to use ... to refer to ../.., .... to refer to ../../.., etc. (up to some small finite number; I don't need bash to process an arbitrarily large number of dots). I.e., if my current directory is /tmp/let/me/out, and I call cd ..., my resulting current directory should be /tmp/let. I don't particularly care if ... etc. show up in ls -a output like . and .. do, but I would like to be able to call cat /tmp/let/me/out/..../phew.txt to print the contents of /tmp/phew.txt.
Pointers to relevant documentation appreciated as well as direct answers. This kind of syntax question is very hard to Google.
I'm using bash 4.3.42, by the way, with the autocd and globstar shell options.
. and .. are genuine directory names. They are not "sort-cuts", aliases, or anything fake.
They happen to point to the same inode as the other name you use. A file or directory can have several names pointing to the same inode, these are usually known as hard links, to distinguish them from symbolic (or soft) links.
If you are on Linux or OS X you can use stat to look at most of the inode metadata - it is what ls looks at. You will see there is an inode number. If you stat . and stat current-directory-name you will see that number is the same.
The one thing that is not held in the inode is the filename - that is held in the directory.
So . and .. reside in the directory on the file system, they are not a figment of the shell's imagination. So, for example, I can use . and .. quite happily from C.
I doubt you can change them - personally I have never tried and I never will. You would have to change what these filenames linked to by editing the directory. If you managed it you would probably do irreparable damage to your file system.
I write this to clarify what has already been written before.
In many file systems a DIRECTORY is a file; a special type of file that the file system identifies as being distinctly a directly.
A directory file contains a list of names that map to files on the disk
A file, including a directly does not have an intrinsic name associated with it (not true in all file systems). The name of a file exists only in a directory.
The same file can have an entry in multiple directories (hard link). The same file can then have multiple names and multiple paths.
The file system maintains in every directory entries for "." and ".."
In such file systems there are always directory ENTRIES for the NAMES "." and "..". These entries are maintained by the file system.
The name "." links to its own directory.
The name ".." links to the parent directory EXCEPT for the top level directory where it links to itself (. and .. thus link to the same directory file).
So when you use "." and ".." as in /dir1/dir2/../dir3/./dir4/whatever,
"." and ".." are processed in the exact same way as "dir1" and "dir2".
This translation is done by the file system; not the shell.
cd ...
Does not work because there is no entry for "..." (at least not normally).
You can create a directory called "..." if you want.
You can actually achieve something like this, though this is an ugly hack:
You can run a command before every command entered to bash, and after every command. For that you trap the DEBUG pseudo signal and set a command to PROMPT_COMMAND, respectively.
trap 'ln -s ../.. ... &>/dev/null | true' DEBUG
PROMPT_COMMAND='rm ...'
With this, it seems like there's an additional entry in the current directory:
pwd
# /tmp/crazy-stuff
ls -a
# . .. ... foo
ls -a .../tmp/crazy-stuff
# . .. ... foo
Though this only works in the current directory, because the symbolic links is deleted after each command invokation. Thus ls foo/bar/... won't work this way.
Another ugly hack would be to "override" mkdir such that it populates every new directory with these symbolic links.
See also the comments on the second answer here, particularly Eliah's: https://askubuntu.com/questions/327126/what-is-a-dot-only-named-folder
Much in the same way that when you cd into some directory subdir, you're actually following a pointer that points to that directory, .. is a pointer added by the OS that points to the parent directory, and I'd imagine . works the same way.
I'm trying to install a grunt template on my computer but I'm having issues. I realized that perhaps something different is happening because of the path given by the Grunt docs, which is
%USERPROFILE%\.grunt-init\
What does that . mean before grunt-init?
I've tried to do the whole import manually but it also isn't working
git clone https://github.com/gruntjs/grunt-init-gruntfile.git "C:\Users\Imray\AppData\Roaming\npm\gru
nt-init\"
I get a message:
fatal: could not create work tree dir 'C:\Users\Imray\AppData\Roaming\npm\.grunt-init"'.: Invalid argument
Does it have to do with this /.? What does it mean?
The \ (that's a backslash, not a slash) is a directory delimiter. The . is simply part of the directory name.
.grunt-init and grunt-init are two distinct names, both perfectly valid.
On Unix-like systems, file and directory names starting with . are hidden by default, which is why you'll often see such names for things like configuration files.
The . is part of a directory name. Filenames can contain . . The \ is a separator between directory names.
Typically, files or directories starting with . are considered "hidden" and/or used for storing metadata. In particular, shell wildcard expansion skips over files that start with ..
For example if you wrote ls -d * then it would not show any files or directories beginning with . (including . and .., the current and parent directories).
Linux hides files and directories whose names begin with dot, unless you use the a (for "all") option when listing directory contents. If this convention is not followed on Windows, your example is probably just a carryover.
It may well be something behind the scenes (later) expects that name to match exactly. While I like things, installers, for example, to just do what I said, I realize that keeping default value is the most tested path.
Directories starting with a dot are invisible by default on xNIX systems. Typically used for configurations files and similar in a users home directory.
\ before " has a special meaning on windows, the error is because windows won't let you create a file containing " as part of its name.
In an empty directory, the following code
Dir.foreach("./") do |file|
puts file
end
returns
.
..
In my understanding . refers to the working directory and .. refers to the parent directory; why does foreach seem to treat them as files within the working directory?
Because they are files within the working directory. The . and .. directories are not magical; they appear the same way any subdirectory does, as entries in the directory. Every directory on a UNIX-type file system has actual directory entries named . and ... So if you don't want to include them when processing a directory, you need to exclude them yourself.
I was trying to get path current path in PHP. I tried looking though phpinfo();, but I haven't found any interesting values which could be used to get path to my script. There is no nice values which I used on Linux, like $_SERVER["PWD"].
Now I'm wondering how I'm supposed to find current path. Maybe some function will work... I really have no idea. Because I don't want to hardcode path to script.
getcwd() is what you are looking for.
It's not entirely clear whether you mean the current working directory, or the path to the current script. For the working directory, see #Taze's answer.
For the current script, the __FILE__ magic constant will give you the full filesystem path to the current file.
Note that these constants take "current file" literally: If you include a file and call __FILE__ there, it will show the included file's path.
The getcwd() method will return the current working directory on success.
<?php
echo getcwd() . "\n";
?>