initial

joplin notion extension/Web Development/Extras/7zip.md

@@ -0,0 +1,111 @@
+7zip
+
+The 7z file format uses a combination of various compression algorithms, with the primary one being LZMA (Lempel-Ziv-Markov chain algorithm). LZMA is known for its high compression ratio and fast decompression. Here is an overview:
+
+- *LZMA/LZMA2:* This is the default and most commonly used algorithm when creating 7z archives. LZMA2 is an improved version of LZMA, offering better multithreading support.
+
+- *PPMd:* Stands for Prediction by Partial Matching, which is good at compressing text data.
+
+- *BCJ/BCJ2:* These are Branch/Call/Jump conversion filters that pre-process executable files to improve compression.
+
+- *DEFLATE:* A widely used compression algorithm that is also used in ZIP file format.
+
+- *BZip2:* Another block-sorting compression algorithm that is particularly effective at compressing large text files.
+
+Here are some technical details of LZMA/LZMA2, in case they are needed for advanced utilization:
+
+- *Dictionary size:* Highly customizable, allowing the compressor to store patterns, which can dramatically affect compression ratio and memory requirements.
+  
+- *Compression speed versus Decompression speed:* These are adjustable; typically, LZMA offers slower compression speeds but fast decompression speeds.
+
+- *Multi-threading support:* LZMA2 in particular can utilize multiple processor cores to improve compression speed on modern computers.
+
+For archival purposes using 7z, it is also possible to enable solid compression, which treats multiple files within the archive as a single data block for potentially better compression ratios.
+
+Encryption algorithm : AES-256
+
+Terminal
+
+https://www.redhat.com/sysadmin/encrypting-decrypting-7zip
+
+Encrypting
+```bash
+$ tar -cf directory.tar <directory>
+
+$ 7z a -p -mhe=on directory.tar.7z directory.tar
+or
+
+7z a -pYourPassword -mhe=on directory.tar.7z directory.tar
+
+```
+Here a means adding files to  archive
+mhe=on means header encryption means metadata like file names will be encrypted too
+For non interactive password typing type password just after `-p` with no space
+
+also  for level of compression
+`7z a path/to/archive.7z -mx=0|1|3|5|7|9 path/to/file_or_directory`
+ 0 means lowest compression while 9 being highest
+
+&nbsp;
+
+**for exluding directories**
+To exclude directories when creating a 7z archive, use the
+-x switch with the ! wildcard operator, and add an r flag (for recursive) to the switch name if the directories might be in subfolders. 
+The basic syntax for creating an archive and excluding a specific directory named exclude_dir is:
+`7z a archive.7z source_dir/ -xr\!exclude_dir/`
+dont forget `\` before `!` as ! is reserved for events
+
+
+Decrypting
+
+```bash
+7z x archive.7z
+```
+here x means extracting
+
+mroe flags
+- `-aoa`: Overwrite All existing files without asking
+- `-aos`: Skip extracting any files that already exist (prevents replacing).
+- `-aou`: Auto-rename the extracted file (e.g., file_1.txt) if the target name exists.
+- `-aot`: Auto-rename the existing file and extract the new one.
+&nbsp;
+
+**for splitting**
+`7z a -v100m archive.7z my_folder/`
+
+for mass compression of folders
+```sh
+#!/bin/bash
+
+# Check if 7z is installed
+if ! command -v 7z &> /dev/null
+then
+    echo "7z command not found! Please install 7zip."
+    exit 1
+fi
+
+# Loop through all directories in the current directory
+for dir in */; do
+    # Make sure it's a directory
+    if [ -d "$dir" ]; then
+        # Remove the trailing slash from the directory name
+        dir_name=${dir%/}
+
+        # Create a .7z archive for each directory
+        echo "Creating archive for $dir_name..."
+        7z a "${dir_name}.7z" "$dir_name"
+    fi
+done
+
+echo "Done!"
+
+```
+
+&nbsp;
+
+to print only filepaths instead of other info
+`7z l -ba archive.7z | grep -oP '(?<=^.{53}).*'`
+from
+https://stackoverflow.com/questions/55355466/7z-list-only-filenames
+to list only top level use this
+`7z l -ba archive.7z | grep -oP '(?<=^.{53}).*' | grep -v '/'`