> For the complete documentation index, see [llms.txt](https://sauravv.gitbook.io/workspace/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sauravv.gitbook.io/workspace/nix-commands.md).

# \*Nix Commands

### Create package

Below command will create a package from files located in different directories & files with and without preserving the directory structure.

`-C` is used to change directory and then include the following file. Without it the directory structure is preserved. The files and folder appear in the root directory

```
tar -czf project-name.tar.gz ./bin/startserver.sh -C build/libs project-1.0.jar -C ../../lib/properties log4j2-project.xml
```

### String Operations

Check null value in strings

```
// Check null value in string
my_var="nixCraft"
if [ -z "$my_var" ]
then
      echo "\$my_var is NULL"
else
      echo "\$my_var is NOT NULL"
fi
```

####  Split Strings

```
// Split and get the last results
$ foo=hadoop-mapreduce-client-core-2.7.3
$ echo ${foo##*-}

// Split and get a substring    
```

### Miscellaneous

**Find jar versions of all jars in a folder from its manifest file**\
*ls | xargs -I {} 'unzip {} META-INF/MANIFEST.MF; version=\`cat META-INF/MANIFEST.MF | grep "Implementation-Version\\|Bundle-Version" | sed "s/Bundle-Version: //" | sed "s/Implementation-Version: //"\`;echo {} -------- $version >> jar-version.txt'*