pmparseunitsstr(3) — Linux manual page


PMPARSEUNITSSTR(3)      Library Functions Manual      PMPARSEUNITSSTR(3)

NAME         top

       pmParseUnitsStr - parse units specification

C SYNOPSIS         top

       #include <pcp/pmapi.h>

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

       cc ... -lpcp

DESCRIPTION         top

       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

       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.,

       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         top

       │              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         top

       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

RETURN VALUE         top

       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         top

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

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-16.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                PMPARSEUNITSSTR(3)

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