I want to sort strings from file; this code compiles well, but it stops working in line 29, when I do words_array[i] = strdup(line);.
From debugger I have "program received signal sigsegv segmentation fault"
#include<stdio.h> #include<stdlib.h> #include<string.h> int comparator ( const void * elem1, const void * elem2 ) { return strcmp( *(const char**) elem1, *(const char**) elem2); } int main() { char filename[]="dane.txt"; FILE* fp; char* line = NULL; size_t len = 0; char** words_array = NULL; int i = 0,j; // number of elements // read list from file if( ( fp = fopen(filename, "r") ) == NULL ) { fprintf(stderr, "Cannot open source file %s!\n", filename); exit(1); } for(; fgets(line, len, fp) != NULL; ++i) { // put word in array words_array = realloc(words_array, sizeof(char*) * (i + 1) ); words_array[i] = strdup(line); } fclose(fp); free(line); // sort it qsort(words_array, i, sizeof(char*), comparator); if( ( fp = fopen(filename, "a+") ) == NULL ) { fprintf(stderr, "Cannot open source file %s!\n", filename); exit(1); } // write to file and free dynamically allocated memory for(j = 0; j < i; ++j) { fprintf(fp, "%s", words_array[j]); free(words_array[j]); } free(words_array); fclose(fp); return 0; } 
fgets(&line, &len, fp) != -1-->fgets(line, len, fp) != NULL, but notice thatlen = 0at this point andlinedoesn't have room to store the string.fgets-->getlinestrcmp( (char*) elem1, (char*) elem2)-->strcmp( *(const char**) elem1, *(const char**) elem2)getline