---
name: "mmv_lookup_value_desc"
section: "3"
platform: "linux"
package: "pcp"
version: "7.2.2-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/mmv_lookup_value_desc"
---

# mmv\_lookup\_value\_desc(3)

find a value in the Memory Mapped Value file

## NAME

**mmv\_lookup\_value\_desc** - find a value in the Memory Mapped Value file

## C SYNOPSIS

**#include \<pcp/pmapi.h\>**\
 **#include \<pcp/mmv\_stats.h\>**

**pmAtomValue \*mmv\_lookup\_value\_desc(void \****addr***,** **const char \****metric***,** **const char \****inst***);**

**cc ... -lpcp\_mmv -lpcp**

## DESCRIPTION

**mmv\_lookup\_value\_desc** searches for the value of the instance identified by the external instance name *inst* of the metric *metric* in the **MMV**(5) file. *addr* is the address returned from **mmv\_stats\_init**().

The pointer returned points to a pmAtomValue union, which is defined as follows:

```
    typedef union {
        __int32_t   l;      /* 32-bit signed */
        __uint32_t  ul;     /* 32-bit unsigned */
        __int64_t   ll;     /* 64-bit signed */
        __uint64_t  ull;    /* 64-bit unsigned */
        float       f;      /* 32-bit floating point */
        double      d;      /* 64-bit floating point */
        char         *cp;   /* char ptr */
	pmValueBlock *vbp;  /* pmValueBlock ptr */
    } pmAtomValue;
```

MMV string values should be set using either of the **mmv\_set\_string** or **mmv\_set\_strlen** routines.

## RETURNS

The function returns the address inside of the memory mapped region on success or NULL on failure.

## SEE ALSO

[**mmv\_stats\_init**(3)](/mmv_stats_init/3.md), [**mmv\_inc\_value**(3)](/mmv_inc_value/3.md) and [**mmv**(5)](/mmv/5.md).