string - Help needed in Segmentation Error in my C code -

i have been trying identify program generates segmentation no avail. need in pin-pointing of strings operations or char pointers causing segmentation fault during runtime. program compiles gives segmentation error during run-time.

#include<curses.h> #include<strings.h> #include<unistd.h>  #include<stdlib.h>  /*implements scrolling headband takes string argument , continously scrolls*/                int main(int argc, char* argv[]) {     /*a substring function return substring of string*/     char *substr(const char *src, int start, int len);     /*appends character given string*/     void append(char* s, char c);     /***check if argument invalid***/     if(argc!=2)     {         puts("invalid number of arguments: usage:headband <string>");     }     /**get headtext string argument argv[1]**/     char *headtext = argv[1];      /*headband(headtext);*/     /*temporary variable store strings execution progresses*/     char temp[100];     /*counter streaming , scolling headband text*/     int count = 0;     /*placeholder temporary headband text*/     char hold[100];     int i;     /*maximum x , y co-ordinates of screen*/     int max_x,max_y;     /*initialize screen ncurses*/     initscr();     /*don't show cursor*/     curs_set(0);     /*get terminal console dimensions*/     getmaxyx(stdscr, max_y, max_x);     /*get console width set default console screen width=80*/     int consolewidth = max_x;     /*clear screen*/     clear();     /*set first value end of string momment*/     temp[0] = '\0';     /*run loop continuously keep scrolling*/     (;;)     {         for(i=0; < strlen(headtext); i++)         {             count++;             /*append headband text character character string hold*/             append(temp, headtext[i]);             move(0,consolewidth - count);             if (consolewidth - count > 0)             {                 mvaddstr(0,console_width-count,temp);                 refresh();             }             else if (consolewidth - count == 0)             {                 strcpy(hold, temp);                 char q;                 int com = i;                 for(;;)                 {                     /*scroll text triming 1 character @ time*/                      /*from left, adding character the*/                     /*right side of text*/                     com = com + 1;                     if (com < strlen(headtext))                     {                         q = headtext[com];                     }                     else                     {                         com = 0;                         q = headtext[com];                         //q = hold[0];                     }                     strcpy(hold, substr(hold, 1, strlen(hold) - 1));                     append(hold, q);                     move(0,0);                     clear();                     mvaddstr(0,0,hold);                     refresh();                     usleep(50);                 }             }             usleep(50);         }     }     return 0; }  /*a substring function return substring of string*/ char * substr(const char *src, int start, int len)  {        char *dest = malloc(len+1);        if (dest)      {         memcpy(dest, src+start, len);              dest[len] = '\0';        }        return dest; }  /*appends character given string*/ void append(char s[], char c) {     int len = strlen(s);     s[len] = c;     s[len+1] = '\0'; } 

i don't know compiler using, here quick guide how debug gcc , gdb:

$ gcc -g file.c -o myexec   # -g flag enables debug info  $ gdb ./myexec 

now in gdb prompt. if need set command line arguments use:

set args <arg1> <arg2> ... 

then run program

run 

once crashes can sorts of things. shows @ point in program error happened. want use these commands:

bt            # prints backtrace / call stack print <expr>  # print value of expression 

there couple of cheat sheets on web, can quick idea @ sorts of commands available.