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: http://www.stsci.edu/~sontag/spicedocs/cspice/prompt_c.html
Дата изменения: Sat Dec 17 06:09:28 2005 Дата индексирования: Mon Apr 11 00:06:46 2016 Кодировка: Поисковые слова: comet tail |
This function prompts a user for keyboard input.
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Variable I/O Description -------- --- -------------------------------------------------- prmptStr I The prompt string to display when asking for input. lenout I Minimum number of characters for response plus one. buffer O The string containing the response typed by a user. The routine also returns a pointer to the output buffer.
prmptStr A character string displayed from the current cursor position which describes the requested input. The prompt string should be relatively short, i.e., 50 or fewer characters, so a response may be typed on the line where the prompt appears. All characters (including trailing blanks) in prmptStr are considered significant and will be displayed. lenout The integer number of characters plus one for the response string.
buffer The user supplied string which holds the response. The string's memory is allocated in the calling routine. The routine returns a pointer to buffer as well as passing the pointer back via an argument.
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This is a utility that allows you to "easily" request information from a program user. The calling program declares an array or allocate memory to contain the user's response to the prompt.
Suppose you have an interactive program that computes state vectors by calling spkezr_c. The program prompts the user for the inputs to spkezr_c. After each prompt is written, the program leaves the cursor at the end of the string as shown here: Enter UTC epoch > _ (The underscore indicates the cursor position). The following program illustrates the aquisition of input values using prompt_c: #include <stdlib.h> #include <stdio.h> #include "SpiceUsr.h" #define STRLEN 32 void main() { SpiceChar utc [STRLEN]; SpiceChar obs [STRLEN]; SpiceChar targ [STRLEN]; SpiceChar * utc1; SpiceChar * obs1; SpiceChar * targ1; /. Call the routine as a subroutine. ./ prompt_c ( "Enter UTC epoch > ", STRLEN, utc ); prompt_c ( "Enter observer name > ", STRLEN, obs ); prompt_c ( "Enter target name > ", STRLEN, targ ); /. Or call the routine as a function. ./ utc1 = ( SpiceChar * ) malloc (STRLEN); obs1 = ( SpiceChar * ) malloc (STRLEN); targ1 = ( SpiceChar * ) malloc (STRLEN); utc1 = prompt_c ( "Enter UTC epoch > ", STRLEN, utc1 ); obs1 = prompt_c ( "Enter observer name > ", STRLEN, obs1 ); targ1= prompt_c ( "Enter target name > ", STRLEN, targ1); /. Now do stuff with your strings. ./ ... }
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1) If the output string has length less than two characters, it is too short to contain one character of output data plus a null terminator, so it cannot be passed to the underlying Fortran routine. In this event, the the error SPICE(STRINGTOOSHORT) is signaled and a null pointer is returned.
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N.J. Bachman (JPL) K.R. Gehringer (JPL) W.L. Taber (JPL) E.D. Wright (JPL)
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-CSPICE Version 1.0.0, 25-JUN-1999 (EDW) (NJB)
Prompt for keyboard input Prompt for input with a user supplied message