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field_buffer(3FORM) field_buffer(3FORM)


form_field_buffer - field buffer control


#include <form.h>

int set_field_buffer(FIELD *field, int buf, const char *value);
char *field_buffer(const FIELD *field, int buffer);

int set_field_status(FIELD *field, bool status);
bool field_status(const FIELD *field);

int set_max_field(FIELD *field, int max);


The function set_field_buffer sets the numbered buffer of the given field to contain a given string:

  • Buffer 0 is the displayed value of the field.
  • Other numbered buffers may be allocated by applications through the nbuf argument of (see field_new(3FORM)) but are not manipulated by the forms library.

The function field_buffer returns a pointer to the contents of the given numbered buffer:

  • The buffer contents always have the same length, and are padded with trailing spaces as needed to ensure this length is the same.
  • The buffer may contain leading spaces, depending on how it was set.
  • The buffer contents are set with set_field_buffer, or as a side effect of any editing operations on the corresponding field.
  • Editing operations are based on the window which displays the field, rather than a string. The window contains only printable characters, and is filled with blanks. If you want the raw data, you must write your own routine that copies the value out of the buffer and removes the leading and trailing spaces.
  • Because editing operations change the content of the buffer to correspond to the window, you should not rely on using buffers for long-term storage of form data.

The function set_field_status sets the associated status flag of field; field_status gets the current value. The status flag is set to a nonzero value whenever the field changes.

The function set_max_field sets the maximum size for a dynamic field. An argument of 0 turns off any maximum size threshold for that field.


The field_buffer function returns NULL on error. It sets errno according to their success:

The routine succeeded.
Routine detected an incorrect or out-of-range argument.

The field_status function returns TRUE or FALSE.

The remaining routines return one of the following:

The routine succeeded.
System error occurred (see errno(3)).
Routine detected an incorrect or out-of-range argument.


ncurses(3NCURSES) and related pages whose names begin “form_” for detailed descriptions of the entry points.


The header file <form.h> automatically includes the header file

When configured for wide characters, field_buffer returns a pointer to temporary storage (allocated and freed by the library). The application should not attempt to modify the data. It will be freed on the next call to field_buffer to return the same buffer. <curses.h>.


These routines emulate the System V forms library. They were not supported on Version 7 or BSD versions.

The set_max_field function checks for an ncurses extension O_INPUT_FIELD which allows a dynamic field to shrink if the new limit is smaller than the current field size.


Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S. Raymond.