I wrote a simple program ramp-io, based on the redshift code, to read and write the xrandr gamma ramps for Linux / X11. This enables me to define my own gamma ramps, and switch ramps quickly from the command line. My preferred ramp is red-inv, dim inverse video with a low colour temperature (more red, less blue), and I set the LCD hardware brightness to maximum to reduce LED PWM flicker. I find this is relatively easy on the eyes for work, compared to the normal glaring white backgrounds.
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Sam's Hacktastic Blog 
Thanks Sam. This helped me make a simple utility to set the colour temperature. It’s not as flexible as yours, but simple enough for my needs. Here’s the basic function:
#include
#include
#include “gamma-randr.h”
/**
* Set colour temperature (1000-25000) and brightness (0.0-1.0) on all screens.
*/
void set_colour_temperature(const int temperature_K, const float brightness)
{
randr_state_t _state;
memset(&_state, 0, sizeof(_state));
randr_state_t *state = &_state;
printf(“Setting temp=%dK, brightness=%1.1f\n”, temperature_K, brightness);
color_setting_t setting;
setting.gamma[0]=1.0;
setting.gamma[1]=1.0;
setting.gamma[2]=1.0;
setting.brightness=brightness;
setting.temperature=temperature_K;
if (randr_init(state) != 0)
die(“failed: randr_init”);
if (randr_start(state) != 0)
die(“failed: randr_start”);
state->crtc_num=-1; // set all screens
randr_set_temperature(state, &setting);
randr_free(state);
}