### Install and Configure Brightness Sync Agent

Source: https://github.com/kfix/ddcctl/wiki/How-to-sync-brightness-of-main-display-with-secondary

Installs the ddcctl binary and sets up a launchd agent to sync brightness every minute. Ensure the binary is in your PATH.

```bash
mkdir -p ~/Library/LaunchAgents
curl -o ~/Library/LaunchAgents/com.zerowidth.launched.sync-brightness.plist http://launched.zerowidth.com/plists/3902c360-bb27-0139-1649-5da0311d64fa.xml
launchctl load -w ~/Library/LaunchAgents/com.zerowidth.launched.sync-brightness.plist
```

--------------------------------

### Download and Install Pre-built Binary

Source: https://context7.com/kfix/ddcctl/llms.txt

Download the latest release binaries, unzip, and copy the ddcctl executable to your system's PATH. Ensure it has execute permissions.

```bash
# Download latest release zip from GitHub
curl -L https://github.com/kfix/ddcctl/releases/latest/download/ddcctl_binaries.zip -o ddcctl_binaries.zip
unzip ddcctl_binaries.zip
cp ddcctl /usr/local/bin/
chmod +x /usr/local/bin/ddcctl
```

--------------------------------

### Multi-Monitor Preset Script with ddcctl.sh

Source: https://context7.com/kfix/ddcctl/llms.txt

Example bash script demonstrating control of multiple monitors using named presets, relative adjustments, and persistent state management.

```bash
#!/bin/bash
# Usage: ddcctl.sh [dim|bright|up|down|volmute|volup|voldown|poweroff]
# State is persisted in ~/.ddc_control_state

hp="ddcctl -d 1"   # HP monitor on display slot 1
len="ddcctl -d 2"  # LEN monitor on display slot 2

# Apply dim preset (night-time)
dim() {
    $hp  -b 42 -c 26
    $len -b 4  -c 9
}

# Apply bright preset (daytime)
bright() {
    $hp  -b 100 -c 75
    $len -b 85  -c 80
}

# Increase both monitors by 10 (capped at 100)
up() {
    newb=$((brightness+10)); [[ $newb -gt 100 ]] && newb=100
    newc=$((contrast+10));   [[ $newc -gt 100 ]] && newc=100
    $hp  -b $newb -c $newc
    $len -b $newb -c $newc
}

# Automatically select preset based on hour of day (7am–7pm = bright)
# Run without arguments for time-based auto-selection
./ddcctl.sh          # auto
./ddcctl.sh dim      # force dim
./ddcctl.sh bright   # force bright
./ddcctl.sh up       # step up
./ddcctl.sh volup    # raise volume

```

--------------------------------

### Install ddcctl via Homebrew

Source: https://github.com/kfix/ddcctl/blob/main/README.md

Use this command to install ddcctl using the Homebrew package manager. Ensure Homebrew is installed on your system.

```bash
brew install ddcctl
```

--------------------------------

### Build ddcctl from Source

Source: https://context7.com/kfix/ddcctl/llms.txt

Compile ddcctl from its source code. Requires Xcode command-line tools. After building, you can install it to /usr/local/bin.

```bash
# Requires Xcode command-line tools
git clone https://github.com/kfix/ddcctl.git
cd ddcctl
make
make install   # installs to /usr/local/bin
```

--------------------------------

### Set Monitor Input Source via ddcctl

Source: https://github.com/kfix/ddcctl/blob/main/README.md

Example of how to set the input source for a specific display. Replace '1' with the desired display number and '17' with the corresponding input source value from the provided table.

```bash
ddcctl -d 1 -i 17
```

--------------------------------

### Build ddcctl from Source

Source: https://github.com/kfix/ddcctl/blob/main/README.md

Follow these steps to build ddcctl from its source code. This requires Xcode to be installed on your macOS system.

```bash
make
```

--------------------------------

### Set RGB Color Gain on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Set the Red, Green, and Blue gain values for the first external display. This example sets a warm color profile by boosting red and reducing blue.

```bash
# Set a warm color profile (boost red, reduce blue)
ddcctl -d 1 -rg 100 -gg 85 -bg 70
```

--------------------------------

### Set DDC Reply Timeout with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

Use `-W` to set the minimum reply wait time in nanoseconds. This is useful for slow monitors or specific GPU setups.

```bash
# Extend reply timeout to 50ms
ddcctl -d 1 -W 50000000 -b ?
```

--------------------------------

### Display ddcctl Help Options

Source: https://github.com/kfix/ddcctl/blob/main/README.md

Run this command to view all available options and usage instructions for ddcctl. This is useful for understanding the tool's capabilities.

```bash
ddcctl -h
```

--------------------------------

### Load Launch Agent

Source: https://context7.com/kfix/ddcctl/llms.txt

Loads a launch agent plist file. Ensure the path to the plist is correct.

```bash
launchctl load -w ~/Library/LaunchAgents/com.example.sync-brightness.plist
```

--------------------------------

### Switch Input Source on Display 2

Source: https://context7.com/kfix/ddcctl/llms.txt

Change the active input source for the second external display to USB-C.

```bash
# Switch display 2 to USB-C
ddcctl -d 2 -i 27
```

--------------------------------

### Set Home Preset with ControlPlane

Source: https://context7.com/kfix/ddcctl/llms.txt

This command sets a medium display preset with a specific input for the 'Home' context in ControlPlane. It uses HDMI input.

```bash
ddcctl -d 1 -b 50 -c 40 -i 17   # medium + HDMI
```

--------------------------------

### Set Office Preset with ControlPlane

Source: https://context7.com/kfix/ddcctl/llms.txt

This command sets a bright display preset with a specific input for the 'Office' context in ControlPlane. It uses DisplayPort input.

```bash
ddcctl -d 1 -b 90 -c 70 -i 15   # bright + DisplayPort
```

--------------------------------

### Set Brightness and Contrast Together

Source: https://context7.com/kfix/ddcctl/llms.txt

Multiple settings can be combined in a single invocation, separated by the inter-command delay.

```APIDOC
## Set Brightness and Contrast Together

### Description
Multiple settings can be combined in a single invocation, separated by the inter-command delay.

### Usage
```bash
# Set both brightness and contrast simultaneously on display 1
ddcctl -d 1 -b 75 -c 50

# "Dim" preset: lower values for night use
ddcctl -d 1 -b 30 -c 20
```
```

--------------------------------

### Reset Brightness and Contrast to Factory Defaults

Source: https://context7.com/kfix/ddcctl/llms.txt

Restore the brightness and contrast settings of the first external display to their factory default values using the VCP reset command.

```bash
ddcctl -d 1 -rbc
```

--------------------------------

### Switch Input Source on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Change the active input source for the first external display. Use the numeric value corresponding to the desired input connector.

```bash
# Switch display 1 to HDMI-1
ddcctl -d 1 -i 17

# Switch display 1 to DisplayPort-1
ddcctl -d 1 -i 15
```

--------------------------------

### Query Current Input Source on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Query the currently active input source for the first external display.

```bash
# Query current input source
ddcctl -d 1 -i ?
```

--------------------------------

### Set Brightness and Contrast Simultaneously

Source: https://context7.com/kfix/ddcctl/llms.txt

Combine brightness and contrast settings in a single command for display 1. Settings are applied sequentially with the configured inter-command delay.

```bash
# Set both brightness and contrast simultaneously on display 1
ddcctl -d 1 -b 75 -c 50

# "Dim" preset: lower values for night use
ddcctl -d 1 -b 30 -c 20
```

--------------------------------

### Contrast (-c)

Source: https://context7.com/kfix/ddcctl/llms.txt

Reads or sets the contrast (VCP control 0x12) of the selected display. Syntax is identical to `-b`.

```APIDOC
## Contrast (-c)

### Description
Reads or sets the contrast (VCP control `0x12`) of the selected display. Syntax is identical to `-b`.

### Usage
```bash
# Query contrast on display 1
ddcctl -d 1 -c ?
# Output: I: VCP control #18 (0x12) = current: 70, max: 100

# Set contrast to 60
ddcctl -d 1 -c 60

# Increase contrast by 5
ddcctl -d 1 -c 5+

# Decrease contrast by 10
ddcctl -d 1 -c 10-
```
```

--------------------------------

### Step Brightness with Karabiner

Source: https://context7.com/kfix/ddcctl/llms.txt

These commands are designed to be bound to key events in Karabiner. Use F1 to decrease brightness and F2 to increase it by 5% steps.

```bash
ddcctl -d 1 -b 5-   # F1 dims
```

```bash
ddcctl -d 1 -b 5+   # F2 brightens
```

--------------------------------

### Manually Sync Brightness with ddcctl and ioreg

Source: https://github.com/kfix/ddcctl/wiki/How-to-sync-brightness-of-main-display-with-secondary

Calculates the current brightness percentage of the primary display using ioreg and bc, then applies it to the secondary display using ddcctl. This script is useful for custom configurations or immediate adjustments.

```bash
/usr/local/bin/ddcctl -d 1 -b $(
  ioreg -c AppleBacklightDisplay \
    | grep "brightness" \
    | sed -nE 's/.*"brightness"={\"min\"=([[:digit:]]+),\"max\"=([[:digit:]]+),\"value\"=([[:digit:]]+)}.*\/scale=10; \3\/\2*100/p' \
    | bc\
)
```

--------------------------------

### Query Contrast on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Query the current contrast level of the first external display. Similar to brightness, it shows the VCP control, current, and maximum values.

```bash
# Query contrast on display 1
ddcctl -d 1 -c ?
# Output: I: VCP control #18 (0x12) = current: 70, max: 100
```

--------------------------------

### Set Color Presets with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

Use `-preset_a`, `-preset_b`, or `-preset_c` to select specific color temperature or picture presets on your monitor. Values are monitor-specific.

```bash
# Dell U2515H: set color preset A to 6500K
ddcctl -d 1 -preset_a 5
```

```bash
# Dell U2515H: set picture mode (preset B) to Movie
ddcctl -d 1 -preset_b 3
```

```bash
# Dell U2515H: query preset_b
ddcctl -d 1 -preset_b ?
```

--------------------------------

### Query Brightness on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Query the current brightness level of the first external display. The output format shows the VCP control, current value, and maximum value.

```bash
# Target display 1
ddcctl -d 1 -b ?
# Output: I: VCP control #16 (0x10) = current: 75, max: 100
```

--------------------------------

### ddcctl Value Setting Grammar

Source: https://context7.com/kfix/ddcctl/llms.txt

Understand the syntax for setting values, including querying (`?`), absolute values (`NN`), and relative adjustments (`NN+`, `NN-`, `+NN`, `-NN`).

```bash
# All equivalent ways to query brightness
ddcctl -d 1 -b ?
```

```bash
# All equivalent relative brightness adjustments (+10)
ddcctl -d 1 -b 10+
ddcctl -d 1 -b +10
```

--------------------------------

### Set Contrast on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Set the contrast of the first external display to an absolute value. Values range from 0 to the maximum supported by the monitor.

```bash
# Set contrast to 60
ddcctl -d 1 -c 60
```

--------------------------------

### Perform Full Monitor Reset with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

The `-reset` command sends the VCP reset code `0x04` to restore all monitor settings to factory defaults.

```bash
ddcctl -d 1 -reset
```

--------------------------------

### Query RGB Color Gain on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Query the current Red, Green, and Blue gain settings for the first external display. Support varies by monitor firmware.

```bash
# Query all three color channels
ddcctl -d 1 -rg ? -gg ? -bg ?
```

--------------------------------

### Dump All VCP Values with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

Use the `-D` flag to iterate through all 256 VCP control codes and display their current and maximum values. This is useful for discovering supported monitor controls.

```bash
ddcctl -d 1 -D
# Output: iterates 0x00..0xFF, printing each register's current/max value
```

--------------------------------

### List Detected External Displays

Source: https://context7.com/kfix/ddcctl/llms.txt

Run ddcctl without any action flags to list detected external displays and display the tool's help information. This helps identify the target display index.

```bash
# List detected external displays (no action flags = prints help + display count)
ddcctl
```

--------------------------------

### Adjust Contrast Relatively on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Increase or decrease the contrast of the first external display by a relative amount. Use '+' for increase and '-' for decrease.

```bash
# Increase contrast by 5
ddcctl -d 1 -c 5+

# Decrease contrast by 10
ddcctl -d 1 -c 10-
```

--------------------------------

### Query Monitor Orientation with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

Use the `-o` flag to query the physical rotation of the display. This is a read-only VCP control.

```bash
ddcctl -d 1 -o
# Output: I: VCP control #170 (0xaa) = current: 1, max: 4
# 1=0°, 2=90°, 3=180°, 4=270°
```

--------------------------------

### Set Brightness on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Set the brightness of the first external display to an absolute value. Values range from 0 to the maximum supported by the monitor.

```bash
# Set brightness to 50 (absolute)
ddcctl -d 1 -b 50
```

--------------------------------

### Query Speaker Volume on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Query the current volume level of the built-in speaker on the first external display.

```bash
# Query current volume
ddcctl -d 1 -v ?
```

--------------------------------

### Reset Brightness and Contrast (-rbc)

Source: https://context7.com/kfix/ddcctl/llms.txt

Sends VCP reset command 0x05 to restore the monitor's factory default brightness and contrast values.

```APIDOC
## Reset Brightness and Contrast (-rbc)

### Description
Sends VCP reset command `0x05` to restore the monitor's factory default brightness and contrast values.

### Usage
```bash
ddcctl -d 1 -rbc
```
```

--------------------------------

### Sync Secondary Display Brightness to Built-in Display (macOS)

Source: https://context7.com/kfix/ddcctl/llms.txt

A one-liner script for macOS that reads the built-in display's brightness percentage and applies it to an external display using ddcctl.

```bash
# One-liner: read macOS backlight brightness percentage and apply to external display 1
/usr/local/bin/ddcctl -d 1 -b $(
  ioreg -c AppleBacklightDisplay \
    | grep "brightness" \
    | sed -nE 's/.*"brightness"=\{\"min\"=([[:digit:]]+),\"max\"=([[:digit:]]+),\"value\"=([[:digit:]]+)\}.*/scale=10; \3/\2*100/p' \
    | bc
)
```

--------------------------------

### Adjust Brightness Relatively on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Increase or decrease the brightness of the first external display by a relative amount. Use '+' for increase and '-' for decrease.

```bash
# Increase brightness by 10
ddcctl -d 1 -b 10+

# Decrease brightness by 20
ddcctl -d 1 -b 20-
```

--------------------------------

### Reset Color Calibration on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Restore the color calibration settings (RGB gain) of the first external display to their factory default values using the VCP reset command.

```bash
ddcctl -d 1 -rrgb
```

--------------------------------

### Check On-Screen Display Status with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

The `-osd` flag queries whether the monitor's OSD menu is currently open. Returns `1` for closed and `2` for active.

```bash
ddcctl -d 1 -osd
# Output: I: VCP control #202 (0xca) = current: 1, max: 2
```

--------------------------------

### Adjust Blue Gain Relatively on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Decrease the Blue gain setting for the first external display by a relative amount.

```bash
# Reduce blue gain by 10
ddcctl -d 1 -bg 10-
```

--------------------------------

### Brightness (-b)

Source: https://context7.com/kfix/ddcctl/llms.txt

Reads or sets the brightness (VCP control 0x10) of the selected display. Accepts an absolute value, a relative increment/decrement, or `?` to query the current value.

```APIDOC
## Brightness (-b)

### Description
Reads or sets the brightness (VCP control `0x10`) of the selected display. Accepts an absolute value, a relative increment/decrement, or `?` to query the current value.

### Usage
```bash
# Query current brightness on display 1
ddcctl -d 1 -b ?
# Output: I: VCP control #16 (0x10) = current: 75, max: 100

# Set brightness to 50 (absolute)
ddcctl -d 1 -b 50

# Increase brightness by 10
ddcctl -d 1 -b 10+

# Decrease brightness by 20
ddcctl -d 1 -b 20-
```
```

--------------------------------

### Select Display (-d)

Source: https://context7.com/kfix/ddcctl/llms.txt

Selects the target external display by its 1-based index. Display 1 is the first external monitor detected by macOS. The built-in MacBook display is always skipped.

```APIDOC
## Select Display (-d)

### Description
Selects the target external display by 1-based index. Display `1` is the first external monitor detected by macOS. The built-in MacBook display is always skipped.

### Usage
```bash
# List detected external displays (no action flags = prints help + display count)
ddcctl

# Target display 1
ddcctl -d 1 -b ?

# Target display 2
ddcctl -d 2 -b ?
```
```

--------------------------------

### Input Source (-i)

Source: https://context7.com/kfix/ddcctl/llms.txt

Switches the active input source (VCP control 0x60). The numeric value corresponds to the physical connector type per the MCCS standard.

```APIDOC
## Input Source (-i)

### Description
Switches the active input source (VCP control `0x60`). The numeric value corresponds to the physical connector type per the MCCS standard.

### Input Mapping
| Input | Value | Input | Value |
|-------|-------|-------|-------|
| VGA-1 | 1 | DisplayPort-1 | 15 |
| DVI-1 | 3 | DisplayPort-2 | 16 |
| DVI-2 | 4 | HDMI-1 | 17 |
| Component 1 | 12 | HDMI-2 | 18 |
| | | USB-C | 27 |

### Usage
```bash
# Switch display 1 to HDMI-1
ddcctl -d 1 -i 17

# Switch display 1 to DisplayPort-1
ddcctl -d 1 -i 15

# Switch display 2 to USB-C
ddcctl -d 2 -i 27

# Query current input source
ddcctl -d 1 -i ?
```
```

--------------------------------

### RGB Gain (-rg, -gg, -bg)

Source: https://context7.com/kfix/ddcctl/llms.txt

Adjusts individual red (VCP 0x16), green (VCP 0x18), and blue (VCP 0x1A) gain channels. Support varies by monitor firmware.

```APIDOC
## RGB Gain (-rg, -gg, -bg)

### Description
Adjusts individual red (VCP `0x16`), green (VCP `0x18`), and blue (VCP `0x1A`) gain channels. Support varies by monitor firmware.

### Usage
```bash
# Query all three color channels
ddcctl -d 1 -rg ? -gg ? -bg ?

# Set a warm color profile (boost red, reduce blue)
ddcctl -d 1 -rg 100 -gg 85 -bg 70

# Reduce blue gain by 10
ddcctl -d 1 -bg 10-
```
```

--------------------------------

### Reset Color (-rrgb)

Source: https://context7.com/kfix/ddcctl/llms.txt

Sends VCP reset command 0x08 to restore the monitor's factory color calibration.

```APIDOC
## Reset Color (-rrgb)

### Description
Sends VCP reset command `0x08` to restore the monitor's factory color calibration.

### Usage
```bash
ddcctl -d 1 -rrgb
```
```

--------------------------------

### Set Speaker Volume on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Set the volume of the built-in speaker on the first external display. Values range from 1 to 254. Monitor firmware must support this feature.

```bash
# Set volume to 20
ddcctl -d 1 -v 20
```

--------------------------------

### Adjust Speaker Volume Relatively on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Increase or decrease the speaker volume on the first external display by a relative amount.

```bash
# Increase volume by 5
ddcctl -d 1 -v 5+
```

--------------------------------

### Toggle Brightness Preset with Alfred

Source: https://context7.com/kfix/ddcctl/llms.txt

This script checks the current brightness and toggles between a dim and bright preset using ddcctl. It's suitable for use in an Alfred workflow's shell action.

```bash
if ddcctl -d 1 -b ? 2>&1 | grep -q "current: [0-9][0-9]$"; then
    ddcctl -d 1 -b 30 -c 20   # dim
else
    ddcctl -d 1 -b 100 -c 75  # bright
fi
```

--------------------------------

### Speaker Volume (-v)

Source: https://context7.com/kfix/ddcctl/llms.txt

Sets the built-in speaker volume (VCP control 0x62). Accepts values 1–254. Support depends on monitor firmware.

```APIDOC
## Speaker Volume (-v)

### Description
Sets the built-in speaker volume (VCP control `0x62`). Accepts values 1–254. Support depends on monitor firmware.

### Usage
```bash
# Set volume to 20
ddcctl -d 1 -v 20

# Query current volume
ddcctl -d 1 -v ?

# Increase volume by 5
ddcctl -d 1 -v 5+
```
```

--------------------------------

### Set Inter-Command Delay with ddcctl

Source: https://context7.com/kfix/ddcctl/llms.txt

The `-w` flag sets the delay in microseconds between DDC commands. Reduce for faster operations or increase if a monitor misses commands.

```bash
# Apply brightness and contrast with a 200ms inter-command delay
ddcctl -d 1 -w 200000 -b 80 -c 60
```

--------------------------------

### VCP Control Code Reference (DDC.h)

Source: https://context7.com/kfix/ddcctl/llms.txt

A reference of key VCP control codes used internally by ddcctl and available for raw testing. These codes correspond to various monitor settings.

```c
#define RESET                      0x04
#define RESET_BRIGHTNESS_AND_CONTRAST  0x05
#define RESET_COLOR                0x08
#define BRIGHTNESS                 0x10
#define CONTRAST                   0x12
#define COLOR_PRESET_A             0x14
#define RED_GAIN                   0x16
#define GREEN_GAIN                 0x18
#define BLUE_GAIN                  0x1A
#define INPUT_SOURCE               0x60
#define AUDIO_SPEAKER_VOLUME       0x62
#define AUDIO_MUTE                 0x8D
#define ORIENTATION                0xAA
#define ON_SCREEN_DISPLAY          0xCA  // read-only
#define OSD_LANGUAGE               0xCC
#define COLOR_PRESET_B             0xDC
#define COLOR_PRESET_C             0xE0
```

--------------------------------

### Mute Speaker on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Mute the built-in speaker on the first external display by setting the audio mute VCP control to ON (value 2).

```bash
# Mute speaker
ddcctl -d 1 -m 2
```

--------------------------------

### Audio Mute (-m)

Source: https://context7.com/kfix/ddcctl/llms.txt

Mutes or unmutes the monitor's built-in speaker (VCP control 0x8D). Value 1 = OFF (unmute), 2 = ON (mute).

```APIDOC
## Audio Mute (-m)

### Description
Mutes or unmutes the monitor's built-in speaker (VCP control `0x8D`). Value `1` = OFF (unmute), `2` = ON (mute).

### Usage
```bash
# Mute speaker
ddcctl -d 1 -m 2

# Unmute speaker
ddcctl -d 1 -m 1
```
```

--------------------------------

### Unmute Speaker on Display 1

Source: https://context7.com/kfix/ddcctl/llms.txt

Unmute the built-in speaker on the first external display by setting the audio mute VCP control to OFF (value 1).

```bash
# Unmute speaker
ddcctl -d 1 -m 1
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.