pmUnitsStr(3) — Linux manual page


PMUNITSSTR(3)             Library Functions Manual             PMUNITSSTR(3)

NAME         top

       pmUnitsStr,  pmUnitsStr_r - convert a performance metric's units into
       a string

C SYNOPSIS         top

       #include <pcp/pmapi.h>

       const char *pmUnitsStr(const pmUnits *pu);
       char *pmUnitsStr_r(const pmUnits *pu, char *buf, int buflen);

       cc ... -lpcp

DESCRIPTION         top

       The encoding of a performance metric's dimensionality and scale uses
       a pmUnits structure; see pmLookupDesc(3).

       As an aid to labeling graphs and tables, or for error messages,
       pmUnitsStr will take a dimension and scale specification as per pu,
       and return the corresponding text string.  The pmUnitsStr_r function
       does the same, but stores the result in a user-supplied buffer buf of
       length buflen, which should have room for at least 60 bytes.  If
       buflen is less than 60 then pmUnitsStr_r returns NULL and buf is not

       For example {1, -2, 0, PM_SPACE_MBYTE, PM_TIME_SEC, 0}, as the value
       of *pu gives the result string Mbyte / sec^2.

       The string value result from pmUnitsStr is held in a single static
       buffer, so the returned value is only valid until the next call to

       If the ``count'' dimension is non-zero, and the ``count'' scale is
       not zero, then the text string will include a decimal scaling factor,
       eg.  count x 10^6.

       As a special case, if all components of the dimension are zero, then
       the ``count'' scale is used to produce the text.  If this scale is
       zero the result is an empty string, otherwise the result is of the
       form x1 0^2.

NOTES         top

       pmUnitsStr returns a pointer to a static buffer and hence is not
       thread-safe.  Multi-threaded applications should use pmUnitsStr_r

SEE ALSO         top

       PMAPI(3), pmAtomStr(3), pmConvScale(3), pmExtractValue(3),
       pmLookupDesc(3), pmPrintValue(3), pmIDStr(3), pmInDomStr(3),
       pmTypeStr(3), pmSemStr(3) and pmUnitsStr(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
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-10-30.)  If you discover any
       rendering problems in this HTML version of the page, or you believe
       there is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot                 PCP                       PMUNITSSTR(3)

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