OK, having taken a better look at what you're doing, I think this is what you were looking for. It loads from a newline-separated file, and can append to it. main() returns a value depending on what option you select, 1 for the first line, etc, etc, or 127 if no selection.
Code:
#include <ncurses.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h> // for isspace()
int barmenu(const char const **array, int row, int col,
int arraylength, int width, int menulength, int selection);
// Removes whitespace from the end of strings
void chomp(char *str)
{
int len=strlen(str);
if(len>0)
while((len>0) && isspace(str[len-1]))
str[--len]='\0';
}
int main(void)
{
char buf[128];
int selection,row=1,col=10,arraylength=0,width=5, menulength=5;
char **testarray=NULL;
FILE *fp=fopen("filename","r");
while(fgets(buf,128,fp) != NULL)
{
chomp(buf); // Remove \n from end of line
if(strlen(buf) > width) width=strlen(buf);
if(!buf[0]) continue; // Ignore blank lines
arraylength++;
// Room for n+1 elements of char * size.
testarray=realloc(testarray, sizeof(char *)*(arraylength+1));
// strdup is an easy str=malloc(strlen(s)+1); strcpy(str,s);
testarray[arraylength-1]=strdup(buf);
}
// The +1 gives us room for a NULL on the end. Makes it easier to find crashes.
testarray[arraylength]=NULL;
fclose(fp);
// If no elements were loaded, it will still be NULL
if(testarray == NULL)
{
fprintf(stderr, "Unable to load options\n");
exit(1);
}
initscr();
noecho();
keypad(stdscr,TRUE);
selection=barmenu((const char const **)testarray,row,col,arraylength,width,menulength,0);
mvprintw(15,0,"Selection= %d",selection);
refresh();
getch();
endwin();
// Add another option to file
fp=fopen("filename","a");
fputs("whatever\n", fp);
fclose(fp);
// We allocated all this stuff, so free it.
for(col=0; col<arraylength; col++) if(testarray[col]) free(testarray[col]);
free(testarray);
// Cannot return -1 to commandline. 127 is the maximum we should return.
if(selection < 0) return(127);
// 0 has special meaning, return n+1
return selection+1;
}
int barmenu(const char const **array, int row, int col,
int arraylength, int width, int menulength, int selection)
{
int counter,offset=0,ky=0;
char formatstring[7];
curs_set(0);
if (arraylength < menulength)
menulength=arraylength;
if (selection > menulength)
offset=selection-menulength+1;
sprintf(formatstring,"%%-%ds",width); // remove - sign to right-justify the menu items
while(ky != 27)
{
for (counter=0; counter < menulength; counter++)
{
if (counter+offset==selection)
attron(A_REVERSE);
mvprintw(row+counter,col,formatstring,array[counter+offset]);
attroff(A_REVERSE);
}
ky=getch();
switch(ky)
{
case KEY_UP:
if (selection)
{
selection--;
if (selection < offset)
offset--;
}
break;
case KEY_DOWN:
if (selection < arraylength-1)
{
selection++;
if (selection > offset+menulength-1)
offset++;
}
break;
case KEY_HOME:
selection=0;
offset=0;
break;
case KEY_END:
selection=arraylength-1;
offset=arraylength-menulength;
break;
case KEY_PPAGE:
selection-=menulength;
if (selection < 0)
selection=0;
offset-=menulength;
if (offset < 0)
offset=0;
break;
case KEY_NPAGE:
selection+=menulength;
if (selection > arraylength-1)
selection=arraylength-1;
offset+=menulength;
if (offset > arraylength-menulength)
offset=arraylength-menulength;
break;
case 10: //enter
return selection;
break;
case KEY_F(1): // function key 1
return -1;
case 27: //esc
// esc twice to get out, otherwise eat the chars that don't work
//from home or end on the keypad
ky=getch();
if (ky == 27)
{
curs_set(0);
mvaddstr(9,77," ");
return -1;
}
else
if (ky=='[')
{
getch();
getch();
}
else
ungetch(ky);
}
}
return -1;
}
Last edited by Corona688; 03-19-2019 at 01:16 PM..
My question is simple: how do I select which data is read by fscanf?
Code:
fscanf(fptr,"%[^\n]", c);
Reads until a newline is detected. I'd like to be able to read a certain line in the text file (contact.txt).
Possibly with user input. Is this possible?
My question is simple: how do I select which data is read by fscanf?
My answer is simple: However you want.
More specifically, scanf cannot seek line 5. (neither can fseek -- they count bytes, not lines.) To get to line 5, read 4 lines:
Code:
int line=5;
char buf[512];
FILE *fp=fopen("file.txt", "r");
while(--line) fgets(buf, 512, fp);
// You are now at line 5.
code_to_read_fifth_line();
Next, rule #1 of C is "never, ever, ever use fscanf". If you absolutely must use scanf, use sscanf. read one line at a time with fgets like I showed you, clean them up with chomp like I showed you, then call sscanf(string, "whatever", arguments);. That will avoid most of scanf's inevitable stumbling blocks.
First problem, scanf has a buffering issue, which is probably why it's not doing what you expect. The first time you call it, it will read until a newline is detected. The second time you call it, it reads until the exact same newline is detected! That newline was never matched, so is still there.
However, fscanf has another problem. What if one of those lines is 1000 bytes but your buffer is only 10? Crash!
You can fix the first issue, to a point. You have to tell fscanf everything it should expect, including the stuff you don't want to keep. Only % codes get read into variables, other stuff gets silently skipped. fscanf(fp, "%[^\r\n]\r\n", c); But if you ever end up with input you didn't specify, fscanf will quite literally choke on it. That's why I specify \r\n here instead of \n. That was a crash issue in software I ported from Windows to UNIX - fscanf had to be amended to accommodate Windows-style carriage returns. \r\n works with both here.
A better example of the way scanf thinks might be sscanf("abcde12345fghijk", "abcde%dfghijk", &number); abcde and fghijk get matched without being stored, only %d is stored because of the %. If you fed it the string "abcdf12345fghijk" it would read "abcd" and stop at f, where it stops agreeing with the string you gave it. The & is required for atomic types - integers and floating point. Strings don't get the & because character arrays are already pointers as far as C's concerned.
Quote:
Thank you for the code. It doesn't do exactly what I want it to do, but it helps. Thanks.
Then what do you want? Your questions are both too specific and not specific enough because you're making hasty choices looking for solutions to problems we don't know about. Like the "inserting text into header file" question as a workaround to actually loading a normal text file. Please explain and I might be able to do what you want. How is telnet involved here? What are you actually doing?
Last edited by Corona688; 03-20-2019 at 01:36 PM..
I'm writing a telnet BBS client. The code i've showed you is the user interface code. I have a telnet function, which, obviously, telnets to a certain address, specified by which line the arrow key selects in the array. My problems are:
1) I have to recompile, every time a BBS is added to the array. Which is an external file.
2) The array is limited to twenty (20) BBSes.. or elements, however you want to look at it
I hope this illustrates what i'm trying to do. And hopefully you understand what i'm trying to do.
Any specific questions?.
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