NAME

       pmParseUnitsStr - parse units specification

C SYNOPSIS

       #include <pcp/pmapi.h>

       int pmParseUnitsStr(const char *string, struct pmUnits *out, double *outMult,
               char **errMsg);

       cc ... -lpcp

DESCRIPTION

       pmParseUnitsStr is designed to encapsulate the interpretation of a  units  (dimension  and
       scale) specification in command line switches for use by the PCP client tools.

       This  function  expects  to  be  called with the unit/scale specification as string.  This
       specification takes the general form  produced  by  pmUnitsStr(3).   Briefly,  the  format
       allows  /-separated  divisor  and dividend, each listing space-separated dimensions/scales
       along the space, time, and count axes.  There are also a few extra possibilities:

       First, multiple  equivalent  sets  of  keywords  are  accepted  for  the  time  and  space
       dimensions,  insensitive to case.  For example, "microseconds", "microsecond", "microsec",
       "us" are considered synonymous, as are "kilobytes", "KB", "KiB", "kiloByte", and so on.

       Second, units may be offered in any order, e.g., ms kb count x 10^3 or count x 10^3 kb ms.
       They  may not be repeated within the denominator or within the numerator.  Each scale/unit
       keyword may be immediately followed by positive or negative exponents, e.g., ^-4.

       Third, numerical scaling factors may  be  supplied.   These  are  factored  together  with
       implicit scale conversions into the final outMult result.

       The  out  and outMult values must both be allocated before calling pmParseUnitsStr(3).  If
       the conversion is successful, pmParseUnitsStr returns 0, and fills in out and outMult with
       the  unit/scales  defined  by  the  input parameter.  If the argument strings could not be
       parsed, it returns a negative status code.

EXAMPLES

                     ┌──────────────────────────────────┬────────────────┬─────────┐
                     │             string               │      out       │ outMult │
                     ├──────────────────────────────────┼────────────────┼─────────┤
                     │2 count                           │ {0,1,0,0,0,0}  │ 0.5     │
                     │count / 7.5 nanosecond            │ {0,1,-1,0,0,0} │ 7.5     │
                     │10 kilobytes / 2.5e2 count x 10^3 │ {1,-1,0,1,3,0} │ 25      │
                     │millisecond / second^2            │ {0,0,-1,0,0,3} │ 1000    │
                     │mib/s                             │ {1,0,-1,2,0,3} │ 1       │
                     └──────────────────────────────────┴────────────────┴─────────┘

BUGS

       For backward compatibility, this interface interprets several traditional computer science
       interpretations  of  space  units  incorrectly  by  the International System of Units (SI)
       standard.

       The accepted unit string - in either singular or plural form  -  and  the  pmParseUnitsStr
       interpretation  for  each are: megabyte(mebibyte), gigabyte(gibibyte), terabyte(tebibyte),
       petabyte(pebibyte), exabyte(exbibyte), zettabyte(zebibyte) and yottabyte(yobibyte).

RETURN VALUE

       A zero status indicates success.  A negative status indicates an error, in which case  the
       errMsg  pointer  will  contain  a  textual  error  message,  which the caller should later
       free(3).

SEE ALSO

       PMAPI(3), pmUnitsStr(3), pmConvScale(3), and pmLookupDesc(3).