---
name: "msr_unpack"
section: "3"
platform: "linux"
package: "libmseed-doc"
version: "2.19.8-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/msr_unpack"
---

# msr\_unpack(3)

Unpacking of Mini-SEED records.

## NAME

msr\_unpack - Unpacking of Mini-SEED records.

## SYNOPSIS

```
#include <libmseed.h>
int msr_unpack ( char *record, int reclen, MSRecord **ppmsr,
                 flag dataflag, flag verbose );
```

**int msr\_unpack\_data ( MSRecord \****msr***, int** *swapflag***, flag** *verbose* **);**

## DESCRIPTION

**msr\_unpack** will unpack a Mini-SEED data record and populate a MSRecord data structure, optionally unpacking data samples.  All multi-byte quantities will be byte-swapped to the host byte order. The MSRecord data structure is described in **[ms\_intro(3)](/ms_intro/3.md)**.

The *reclen* parameter specifies the length of the data record pointed to by *record* in bytes.

If the *\*ppmsr* pointer is NULL a new MSRecord will be allocated, if not the existing MSRecord will be reinitialized and reused destroying any previous contents.  The *ppmsr* pointer itself must not be NULL.

If the *dataflag* flag is not zero any data samples in the record will be unpacked/decompressed.  The following data encoding formats are supported: ASCII, INT16, INT32, FLOAT32, FLOAT64, STEIM1 and STEIM2.  The MSRecord.datasamples pointer will be set appropriately and the samples will be either ASCII, 32-bit integers, 32-bit floats or 64-bit floats with the same byte order as the host machine. MSRecord.numsamples will be set to the actual number of samples unpacked/decompressed.  MSRecord.sampletype will indicated the sample type as either 'a' (ASCII), 'i' (32-bit integers), 'f' (32-bit floats) or 'd' (64-bit doubles).  The size of each sample type in bytes is returned by the get\_samplesize(3) lookup routine.

The *verbose* flag controls verbosity, a value of zero will result in no diagnostic output.

**msr\_unpack\_data** will unpack the data samples for an already parsed MSRecord structure from the original record available at the *MSRecord-\>record* pointer.  Normally this is called by **msr\_unpack** when the *dataflag* is not zero, but it can be useful when the program needs to first unpack the header of a record and decide later if the samples are needed.  If called independently the caller must determine if byte swapping of data samples is needed.

## UNPACKING OVERRIDES

The following macros and environment variables effect the unpacking of Mini-SEED:

```
Macros:
MS_UNPACKHEADERBYTEORDER(X)
MS_UNPACKDATABYTEORDER(X)
MS_UNPACKDATAFORMAT(X)
MS_UNPACKDATAFORMATFALLBACK(X)
Environment variables:
UNPACK_HEADER_BYTEORDER
UNPACK_DATA_BYTEORDER
UNPACK_DATA_FORMAT
UNPACK_DATA_FORMAT_FALLBACK
```

The UNPACK\_HEADER\_BYTEORDER and UNPACK\_DATA\_BYTEORDER macros and variables force the byte order of the header and data respectively. They could be set to either 0 (little endian) or 1 (big endian).  See **[ms\_intro(3)](/ms_intro/3.md)** for a description of how libmseed determines a records byte order.

The UNPACK\_DATA\_FORMAT macro and variable forces the encoding format, this should be set to any of the supported formats codes (i.e. 10 = Steim-1 compression).

The UNPACK\_DATA\_FORMAT\_FALLBACK macro and variable defines an encoding format that will be used when the SEED data record does not indicate the format, i.e. the record does not include a 1000 blockette.  By default the fallback encoding format is 10 (Steim-1 compression).  If this default is invoked and the byte order of the data is unspecified big endian byte order will be assumed.  If a data record does not include a 1000 blockette it is not Mini-SEED, the capability to read these records is included only to support legacy data.

## RETURN VALUE

On the successful parsing of a record **msr\_unpack** returns MS\_NOERROR and populates the MSRecord struct at \*ppmsr.  On error **msr\_unpack** returns a libmseed error code (defined in libmseed.h)

## EXAMPLE

Skeleton code for unpacking a Mini-SEED record with [msr\_unpack(3)](/msr_unpack/3.md):

```
main() {
  MSRecord *msr = NULL;
  char *record;
  int reclen;
  int retcode;
  record = recordptr;   /* pointer to Mini-SEED record */
  reclen = 4096;        /* 4096 byte record length */
  /* Unpack record header and data samples */
  retcode = msr_unpack (record, reclen, &msr, 1, verbose);
  if ( retcode != MS_NOERROR )
    fprintf (stderr, "Error parsing record\n");
  else
    printf ("Unpacked %d samples0, msr->numsamples);
  /* Print record information */
  msr_print (msr, verbose);
  msr_free (&msr);
}
```

## SEE ALSO

**[ms\_intro(3)](/ms_intro/3.md)**, **[msr\_pack(3)](/msr_pack/3.md)** and **[msr\_print(3)](/msr_print/3.md)**.

## AUTHOR

```
Chad Trabant
IRIS Data Management Center
```