Shell Script to Create Empty Files with All Possible Permissions

shell script to create empty files with all possible permissions

Do a loop:

for ((i=0; i < 512; i++)); do 
    mod=$(printf "%03o" "$i"); 
    touch ${mod}.txt; chmod $mod $mod.txt; 
done

Rather than trying to construct the names, if you want the names to look like the output of ls -l, just do something like

for ((i=0; i < 512; i++)); do
    mod=$(printf "%03o" "$i") 
    touch ${mod}.txt
    chmod $mod $mod.txt
    n=$(ls -l $mod.txt | cut -b1-10)
    mv -- $mod.txt "$n.txt"
done

How can I create an empty file at the command line in Windows?

Without redirection, Luc Vu or Erik Konstantopoulos point out to:

copy NUL EMptyFile.txt
copy /b NUL EmptyFile.txt

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"How to create empty text file from a batch file?" (2008) also points to:

type NUL > EmptyFile.txt
# also
echo. 2>EmptyFile.txt
copy nul file.txt > nul # also in qid's answer below
REM. > empty.file
fsutil file createnew file.cmd 0 # to create a file on a mapped drive

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Nomad mentions an original one:

C:\Users\VonC\prog\tests>aaaa > empty_file
'aaaa' is not recognized as an internal or external command, operable program or batch file.

C:\Users\VonC\prog\tests>dir

 Folder C:\Users\VonC\prog\tests

27/11/2013  10:40    <REP>          .
27/11/2013  10:40    <REP>          ..
27/11/2013  10:40                 0 empty_file

In the same spirit, Samuel suggests in the comments:

the shortest one I use is basically the one by Nomad:

.>out.txt

It does give an error:

'.' is not recognized as an internal or external command

But this error is on stderr. And > only redirects stdout, where nothing have been produced.

Hence the creation of an empty file.

The error message can be disregarded here. Or, as in Rain's answer, redirected to NUL:

.>out.txt 2>NUL

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(Original answer, November 2009)

echo.>filename

(echo "" would actually put "" in the file! And echo without the '.' would put "Command ECHO activated" in the file...)

Note: the resulting file is not empty but includes a return line sequence: 2 bytes.

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This discussion points to a true batch solution for a real empty file:

 <nul (set/p z=) >filename

 dir filename
 11/09/2009  19:45                 0 filename
 1 file(s)                         0 bytes

The "<nul" pipes a nul response to the set/p command, which will cause the
variable used to remain unchanged. As usual with set/p, the string to the
right of the equal sign is displayed as a prompt with no CRLF.

Since here the "string to the right of the equal sign" is empty... the result is an empty file.

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The difference with cd. > filename (which is mentioned in Patrick Cuff's answer and does also produce a 0-byte-length file) is that this "bit of redirection" (the <nul... trick) can be used to echo lines without any CR:

<nul (set/p z=hello) >out.txt
<nul (set/p z= world!) >>out.txt
dir out.txt

The dir command should indicate the file size as 11 bytes: "helloworld!".

Bash CLI: Is there a way to simultaneously create and set permissions on a file without repeating the filename?

If you are getting a permissions error when you run your command, that suggests that you do not have permissions to create files where you're trying to create the file. Regarding the rest of your question:

As BroLow said, you can use umask to affect the default permissions of files created in your session. However, this can be inconvenient, particularly if you only want the new permissions in effect for a single command.

You can use the install command to create and set permissions on a file:

install -m <mode> -o <owner> -g <group> <srcfile> <destination>

If you want to create an empty file, you can use /dev/null as a source:

install -m 644 /dev/null <destination>

perserve file permissions when distributing from *nix to Windows

In Windows, all of a user's folders are private by default. In order to share files with other users you must explicitly choose to use one of the standard Public folders, or set up a shared folder of your own.

For this reason, the usual convention is for extracted files to inherit the same permissions as the folder they were extracted into. If the user has extracted the files into a shared folder, it should be safe to assume that they did so deliberately because they want the files to be shared.

Is it possible to create a script to save and restore permissions?

hm. so you need to
1) read file permissions
2) store them somehow, associated to each file
3) read your stored permissions and set them back

not a complete solution but some ideas:

stat -c%a filename
>644

probably in combination with

find -exec

to store this information, this so question has some interesting ideas. basically you create a temporary file structure matching your actual files, with each temp file containing the file permissions

to reset you iterate over your temp files, read permissions and chmod the actual files back.

How to delete files/subfolders in a specific directory at the command prompt in Windows

You can use this shell script to clean up the folder and files within C:\Temp source:

del /q "C:\Temp\*"
FOR /D %%p IN ("C:\Temp\*.*") DO rmdir "%%p" /s /q

Create a batch file (say, delete.bat) containing the above command. Go to the location where the delete.bat file is located and then run the command: delete.bat

Create a new empty file from linux command line with same permissions and ownership?

touch newfile
chmod `stat -c %a originalfile` newfile
chown `stat -c %U originalfile`:`stat -c %G originalfile` newfile

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