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gd_alter_spec, gd_malter_spec — modify a field in a Dirfile


#include <getdata.h>

int gd_alter_spec(DIRFILE *dirfile, const char *line, int recode);

int gd_malter_spec(DIRFILE *dirfile, const char *line, const char *parent, int recode);


The gd_alter_spec() function modifies the field described by the field specification line in line to the dirfile specified by dirfile. The gd_malter_spec() function behaves similarly, but modifies the metafield under the field indicated by the field code parent. Field specification lines are described in detail in dirfile-format(5).

The name of the field to be modified, which must already exist, will be obtained from the field specification line. When adding a metafield, line should only contain a field specification, and not a /META directive.

If the modified field is of type RAW and the recode argument is non-zero, the binary file associated with the field will be converted for changes in data type and samples-per-frame. In this case, the field’s I/O pointer will be reset to the beginning-of-frame. If recode is zero, no binary file conversion will take place.

If the modified field is of type LINTERP and the recode argument is non-zero, the look-up table file will be moved if line specifies a different path, overwriting an existing file with the new pathname, if present. If the field specified by field_code is of type other than RAW or LINTERP, the recode argument is ignored.

Passing these functions a directive line instead of a field specification line will result in a syntax error. These functions never call the registered parser callback function, even if line contains a syntax error.


On success, gd_alter_spec() and gd_malter_spec() return zero. On error, it returns a negative-valued error code. Possible error codes are:

The specified dirfile was opened read-only.


The library was unable to allocate memory.


The field specified in line was not found, or the parent field code was not found.


The supplied dirfile was invalid.


A syntax error was encountered in line.


An I/O error occurred while translating the binary file associated with a modified RAW field, or an I/O error occurred while attempting to rename a LINTERP table file.


The supplied line was longer than the parser was able to deal with. Line lengths are limited by the storage size of size_t.


The metadata of the fragment was protected from change. Or, a request to translate the binary file associated with a RAW field was attempted, but the data of the fragment was protected.


The encoding scheme of the indicated format specification fragment is not known to the library. As a result, the library was unable to translate the binary file be associated with a modified RAW field.


The encoding scheme of the indicated format specification fragment does not support translating the empty binary file associated with a modified RAW field.

The error code is also stored in the DIRFILE object and may be retrieved after this function returns by calling gd_error(3). A descriptive error string for the error may be obtained by calling gd_error_string(3).


The functions dirfile_alter_spec() and dirfile_malter_spec() appeared in GetData-0.5.0.

In GetData-0.7.0, these functions were renamed to gd_alter_spec() and gd_malter_spec.()

In GetData-0.10.0, the error return from these functions changed from -1 to a negative-valued error code.


Any of the gd_alter_<entry-type> functions (e.g., gd_alter_bit(3)), gd_alter_spec(3), gd_error(3), gd_error_string(3), gd_metaflush(3), gd_open(3), dirfile-format(5)