Update Command (u)

The u (update) command updates files in archives with fine-grained control over which files are updated, added, or refreshed based on timestamps and existence.

Syntax

7z u [<switches>...] <archive_name> [<file_names>...] [@listfile]

Description

The update command provides sophisticated archive maintenance by:

Updating existing files with newer versions
Adding new files not in the archive
Skipping files that haven’t changed
Supporting complex update modes
Preserving archive structure and metadata

The main difference between a (add) and u (update): the a command always adds/updates files, while u compares timestamps and only updates newer files by default.

Common Options

archive_name

string

required

Name of the archive to update. Must already exist.

file_names

string

Files or directories to update. Supports wildcards.

-u{Action}

string

Set update action mode. Controls behavior for different file states.Format: -u[-][p#][q#][r#][x#][y#][z#][!newArchiveName]See Update Modes below.

-t{Type}

string

Set archive type.Example: -t7z

-mx{N}

number

Set compression level (0-9).

-p{Password}

string

Set password for encrypted archives.

-r

flag

Recurse subdirectories.

-x{Pattern}

string

Exclude files by pattern.

-i{Pattern}

string

Include files by pattern.

-w{path}

string

Set working directory.

Update Modes

The -u switch controls update behavior with a complex but powerful syntax:

-u[-][p#][q#][r#][x#][y#][z#][!newArchiveName]

State Codes

Each letter represents a file state:

Code	State	Description
`p`	File exists in archive and on disk	Both versions exist
`q`	File exists in archive only	Deleted from disk
`r`	File exists on disk only	New file not in archive
`x`	File in archive is newer	Archive version is newer
`y`	File on disk is newer	Disk version is newer
`z`	Files are same age	Timestamps match

Action Numbers

Each state can have an action:

Number	Action
0	Ignore this file
1	Copy from archive to temp archive
2	Copy from disk to temp archive
3	Copy from both (archive and disk)

Default Update Mode

Without -u, the update command uses:

-up0q0r2x1y2z1

Meaning:

p0 - If in both: ignore (no update)
q0 - If in archive only: ignore (keep in archive)
r2 - If on disk only: add from disk
x1 - If archive is newer: keep archive version
y2 - If disk is newer: update from disk
z1 - If same age: keep archive version

Examples

Basic update (newer files only)

7z u archive.7z files/

Output:

7-Zip 23.01 (x64) : Copyright (c) 1999-2023 Igor Pavlov : 2023-06-20

Scanning the drive:
3 folders, 12 files, 45678 bytes (45 KiB)

Updating archive: archive.7z

Items to compress: 5


Files read from disk: 5
Archive size: 25678 bytes (26 KiB)
Everything is Ok

Update with maximum compression

7z u -mx=9 archive.7z files/

Update specific files

7z u archive.7z updated_file.txt

Update all text files

7z u archive.7z *.txt -r

Synchronize archive with directory

7z u -uq0r2x2y2z0!sync.7z archive.7z files/

This creates sync.7z that exactly matches the files/ directory.

Update and delete removed files

7z u -up1q0r2x1y2z1 archive.7z files/

Advanced Update Modes

Synchronization Mode

Create an archive that exactly mirrors a directory:

7z u -uq0r2x2y2z0!synced.7z original.7z files/

q0 - Remove files deleted from disk
r2 - Add new files from disk
x2 - Use newer file (from disk if disk is newer)
y2 - Use newer file (from disk if disk is newer)
z0 - When same, ignore (keeps archive version)

Incremental Backup

Update only changed files:

7z u -up0q3r2x2y2z0 archive.7z files/

Freshen Existing Files

Update only files that already exist in archive:

7z u -up0q0r0x1y2z1 archive.7z files/

r0 - Don’t add new files
y2 - Update with newer files from disk

Add New Files Only

Add files not in archive, don’t update existing:

7z u -up0q0r2x0y0z0 archive.7z files/

p0 - Ignore files in both
r2 - Add files only on disk

Complex Examples

Update with password

7z u -p archive.7z files/

Prompts for password:

Enter password (will not be echoed):

Update excluding patterns

7z u archive.7z files/ -x!*.tmp -x!*.bak

Update with new compression method

7z u -m0=LZMA2 -md=64m archive.7z files/

Update and show differences

7z u -bb2 archive.7z files/

Conditional update based on size

# Update only files larger than 1MB
find files/ -type f -size +1M | 7z u archive.7z @stdin

Update multiple archives

for archive in *.7z; do
    7z u "$archive" files/
done

Update vs Add Command

Feature	Update (u)	Add (a)
Check timestamps	Yes, by default	No
Skip unchanged files	Yes	No
Update modes	Configurable	Simple
Performance	Faster (skips unchanged)	Slower (processes all)
Use case	Incremental updates	Create/full refresh

When to Use Update

Incremental backups - Only backup changed files
Syncing archives - Keep archive matching directory
Efficiency - Skip unchanged files to save time
Selective updates - Complex update logic needed

When to Use Add

Creating archives - New archive from scratch
Full refresh - Rebuild entire archive
Simplicity - Don’t need timestamp checking
Force update - Update all files regardless of timestamp

Scripting Examples

Daily Incremental Backup

#!/bin/bash
DATE=$(date +%Y%m%d)
ARCHIVE="backup-${DATE}.7z"
SOURCE="/home/user/documents"

if [ -f "$ARCHIVE" ]; then
    # Update existing archive
    7z u "$ARCHIVE" "$SOURCE" -up0q3r2x2y2z0
else
    # Create new archive
    7z a "$ARCHIVE" "$SOURCE"
fi

Smart Update Script

#!/bin/bash
# Update archive only if source files changed

ARCHIVE="archive.7z"
SOURCE="files/"
LOCKFILE="/tmp/archive.lock"

if [ -f "$LOCKFILE" ]; then
    echo "Update already in progress"
    exit 1
fi

touch "$LOCKFILE"
trap "rm -f $LOCKFILE" EXIT

if [ -f "$ARCHIVE" ]; then
    echo "Updating $ARCHIVE..."
    7z u -bb1 "$ARCHIVE" "$SOURCE"
    if [ $? -eq 0 ]; then
        echo "Update successful"
    else
        echo "Update failed with exit code $?"
        exit 1
    fi
else
    echo "Archive not found, creating new archive"
    7z a "$ARCHIVE" "$SOURCE"
fi

Synchronize Directory to Archive

#!/bin/bash
# Create archive that exactly mirrors directory

SOURCE="/data/important"
ARCHIVE="/backup/important.7z"
TEMP_ARCHIVE="/backup/temp.7z"

# Create synchronized copy
if [ -f "$ARCHIVE" ]; then
    7z u -uq0r2x2y2z0!"$TEMP_ARCHIVE" "$ARCHIVE" "$SOURCE"
    if [ $? -eq 0 ]; then
        mv "$TEMP_ARCHIVE" "$ARCHIVE"
        echo "Archive synchronized with source"
    fi
else
    7z a "$ARCHIVE" "$SOURCE"
fi

Performance Tips

Use update instead of recreating - Much faster for large archives
Enable multi-threading - Add -mmt=on for faster compression
Adjust compression level - Use -mx=1 for faster updates
Use solid archives carefully - Solid mode requires recompression
Skip unchanged files - Default behavior saves significant time

For solid archives (-ms=on), updating files requires recompressing the entire solid block, which can be slow. Non-solid archives allow updating individual files independently.

The update command requires the archive to already exist. Use the a (add) command to create a new archive.

To see which files would be updated without actually updating:

7z u -bb2 -bd archive.7z files/ > update_preview.log 2>&1

Check the log before running the actual update.

Add Command (a) - Create or add to archives
Delete Command (d) - Remove files from archives
List Command (l) - View archive contents

Getting Started

Command Reference

Compression Methods

Archive Formats

Advanced Usage

​Syntax

​Description

​Common Options

​Update Modes

​State Codes

​Action Numbers

​Default Update Mode

​Examples

​Basic update (newer files only)

​Update with maximum compression

​Update specific files

​Update all text files

​Synchronize archive with directory

​Update and delete removed files

​Advanced Update Modes

​Synchronization Mode

​Incremental Backup

​Freshen Existing Files

​Add New Files Only

​Complex Examples

​Update with password

​Update excluding patterns

​Update with new compression method

​Update and show differences

​Conditional update based on size

​Update multiple archives

​Update vs Add Command

​When to Use Update

​When to Use Add

​Scripting Examples

​Daily Incremental Backup

​Smart Update Script

​Synchronize Directory to Archive

​Performance Tips

​Related Commands

Build docs developers (and LLMs) love

Syntax

Description

Common Options

Update Modes

State Codes

Action Numbers

Default Update Mode

Examples

Basic update (newer files only)

Update with maximum compression

Update specific files

Update all text files

Synchronize archive with directory

Update and delete removed files

Advanced Update Modes

Synchronization Mode

Incremental Backup

Freshen Existing Files

Add New Files Only

Complex Examples

Update with password

Update excluding patterns

Update with new compression method

Update and show differences

Conditional update based on size

Update multiple archives

Update vs Add Command

When to Use Update

When to Use Add

Scripting Examples

Daily Incremental Backup

Smart Update Script

Synchronize Directory to Archive

Performance Tips

Related Commands