-Gets the memory usage from system.
-On Linux, the information is taken from +/proc/meminfo+.
-
-These values can also be expressed in percentages with the +percentage_used+,
-+percentage_free+ and +percentage_shared+ formats.
-
-If a +critical_low_threshold+ is defined, the output will be colored using
-+color_bad+. The unit of this threshold is defined by the unit given in
-+critical_threshold_type+, which can be one of "bytes_free", "bytes_avail",
-"percentage_free" and "percentage_avail". Additionally, the former two can be
-prefixed with one of "k", "m", "g" or "t" to change the exact unit.
-For example, setting critical_low_threshold to 2 and threshold_type to "gbytes_avail"
-causes available memory below 2 GiB to be colored with +color_bad+. The
-defaults are "percentage_avail" with a threshold of 0.
-Furthermore, the format used when the threshold is reached can be customized
-using the option +critical_format_below_threshold+.
-Same applies to +degraded_low_threshold+, +degraded_threshold_type+ and
-+degraded_format_below_threshold+ using +color_degraded+.
-
-The most common one is:
-"used memory" = "total memory" - "free memory" - "buffers" - "cache"
-This is the default in i3status. Some other programs use
-"used memory" = "total memory" - "available memory"
-You can disable this behavior using +use_available_memory+.