Monthly Archives: November 2016

Using .tgz files 1

 in Bash  tagged compress / create / extract / tar.gz / tgz by

Create

To create a .tgz file, we used tar with the following parameters -czf:

  • -c or --create will create a new archive.
  • -z– or --gzip or --gunzip or --ungzip will filter the archive through gzip and compress it.
  • -f or --file=ARCHIVE will use archive file or device ARCHIVE. If this option is not given, tar will first examine the environment variable TAPE. If it is set, its value will be used as the archive name. Otherwise, tar will assume the compiled-in default.

Example:


tar -czf $ARCHIVE_FILE_NAME.tgz $PATH_TO_COMPRESS;

Please note that the order of the parameters will not change the result.

Extract

To extract a .tgz or .tar.gz file using tar we used the following parameters -xzf:

  • -x or --extract --get will extract the files from the archive. Arguments are optional. When given, they specify names of the archive members to be extracted.
  • -z– or --gzip or --gunzip or --ungzip will filter the archive through gzip and decompress it.
  • -f or --file=ARCHIVE will use archive file or device ARCHIVE. If this option is not given, tar will first examine the environment variable TAPE. If it is set, its value will be used as the archive name. Otherwise, tar will assume the compiled-in default.

Example:


tar -xzf $ARCHIVE_FILE_NAME.tgz;

GNU/Linux find: Get results relative to the directory searching in, instead of directory shell is in

 in Bash  tagged find / relative / sub-shell by

Recently we wanted to create a list of files that could be found in a specific folder.
For that list we wanted the paths of the files to be relative to the folder we were searching in, instead of them being relative to the folder our shell was currently in.

To achieve that, we used cd to navigate into that folder and searched from there locally.
We used a sub-shell to achieve this, which was not needed, but because we did not want to change the current directory of our shell, it was needed.

The command was as follows:

(cd toThe/Path/WeAre/Interested/In && find .)

instead of:

find toThe/Path/WeAre/Interested/In

Since we were interested in getting all files, we did not put any filters on find.
Of course you can use find normally and modify it as you please.

Finally, since we wanted the list of files to be saved in a text file, we redirected the output of the above command to a file in the current working directory

(cd toThe/Path/WeAre/Interested/In && find .) > interestingFiles.txt

Copy a symbolic link without traversing it

 in Bash  tagged cp / symbolic link by

Recently we needed to copy a Symbolic Link on a disk image we would deploy on an embedded device.
For this reason it was important for us to copy the Symbolic Link and not the file it was pointing to as that link would become valid once the machine would boot from the image.

To achieve that we used -P which instructs cp to never follow symbolic links in source. In other words it would not traverse the symbolic link and copy the symbolic link itself.

Notes:

  • --no-dereference is the same as -P.
  • -P uses a capital P.

 

Delete all files and keep the directory structure

 in Bash / GNU/Linux  tagged delete / find by

Scenario

You have a complex folder structure and you want to remove all files and at the same time keep all folders intact.

We will present one method, using two variations of it that can achieve the above.
The method uses the GNU find command to find all files and delete them one by one.

Variation A

find . ! -type d -exec rm '{}' \;

This above command will search in the current directory and sub-directories for anything that is not a folder and then it will delete them.

  • find . – Searches in this folder, since we did not define depth, it will search in all sub-folders as well
  • ! -type d – type d instructs find to match all Directories, by adding the ! in front of the instruction it negates the result and instructs find to match anything but the Directories
  • -exec rm '{}' \; – for every result, the command after exec is executed. The filename replaces '{}' so that the results get deleted one by one.

Variation B

find . ! -type d -delete

In this example, we replaced -exec rm '{}' \; with the simpler to remember directive of -delete.