c - Value disappearing outside of while loop, even though saving to a malloc variable -

i've created struct called utype contains different variables. if want t call utype->t.

now, i'm using fgets retrieve data input file.

the code is:

#include "read_file.h"  int read_file(int argc, char* argv[], utype* u_coarse){     int i;     int num_length = 1024;     file *input_file;     char buffer[num_length];     char *end_of_file;     char *lines = null;     char *lines_temp;     int  num_time_segments=0;     double testest=0;      (i=0; i<num_length; i++){         buffer[i]=' ';     }     input_file = fopen(argv[1], "r");     end_of_file = fgets(buffer, num_length, input_file);     while (end_of_file != null){          if (end_of_file[0]!= '\n' && end_of_file[0]!='%'){             lines = strtok(end_of_file, "=");             if (lines[strlen(lines)-1] == ' '){                 lines[strlen(lines)-1] = '\0';             }             lines_temp = strtok(null, "=");             if (lines_temp[0] == ' '){                 (i=1; i<strlen(lines_temp); i++){                     lines_temp[i-1] = lines_temp[i];                 }                 lines_temp[strlen(lines_temp)-2] = '\0';             }else{                 lines_temp[strlen(lines_temp)-1] = '\0';             }             if (strcmp(lines, "t") == 0){                 u_coarse->ultimatet = atof(lines_temp);             }         //  printf("%g\n", testest);                                                                                                                                    }      } //  printf("%g\n", testest);                                                                                                                                    //  u_coarse->burn_time = testest;                                                                                                                                   fclose(input_file);      return num_time_segments; 

after call read_file function, try print

u_coarse->ultimatet 

but says

conditional jump or move depends on uninitialised value(s) 

when use valgrind. i've been trying figure out why it's giving me memory error while now. appreciated.

edit may 31, 2015:

thank input. i'm attaching adjusted code did improvements. still same error before. valgrind says:

==6485== memcheck, memory error detector ==6485== copyright (c) 2002-2012, , gnu gpl'd, julian seward et al. ==6485== using valgrind-3.8.1 , libvex; rerun -h copyright info ==6485== command: ../bin/main.x ../ ../example_input.inp ==6485==  ==6485== conditional jump or move depends on uninitialised value(s) ==6485==    @ 0x3bfe249cf0: __printf_fp (in /lib64/libc-2.12.so) ==6485==    0x3bfe24589f: vfprintf (in /lib64/libc-2.12.so) ==6485==    0x3bfe24f189: printf (in /lib64/libc-2.12.so) ==6485==    0x406cf1: main (main.c:23) 

where:

main.c:23  

is i'm printing out :

u_coarse->ultimatet 

edited code:

#include "read_file.h"  int read_file(int argc, char* argv[], utype* u_coarse){      int i;     int num_length = 1024;     file *input_file;     char buffer[num_length];     char *current_line;     char *lines = null;     char *lines_temp;     int  num_time_segments=0;     size_t length;     size_t length_temp;      memset(buffer, ' ', sizeof(buffer) -1);     buffer[sizeof(buffer) - 1] = '\0';     input_file = fopen(argv[1], "r");     if (input_file == null){         perror("error");         exit( exit_failure);     }else{         while ( current_line =  fgets(buffer, sizeof(buffer), input_file)){             if (current_line[0]!= '\n' && current_line[0]!='%'){                 lines = strtok(current_line, "=");                 if (lines == null){                     perror("error");                     exit( exit_failure );                 }                 length = strlen(lines);                 if (lines[length-1] == ' '){                     lines[length-1] = '\0';                 }                 lines_temp = strtok(null, "=");                 if (lines_temp == null){                     perror("error");                     exit( exit_failure );                 }                 length_temp = strlen(lines_temp);                 if (lines_temp[0] == ' '){                     memmove(lines_temp, lines_temp +1, length_temp);                 }else{                     lines_temp[length_temp-1] = '\0';                 }                 if (strcmp(lines, "t") == 0){                     u_coarse->ultimatet = atof(lines_temp);                 }             }         }     }     return num_time_segments; } 

my main.c file is:

int main(int argc, char *argv[]) {      utype *u_coarse = (utype*)malloc(sizeof(utype));                               int num_time_segments = read_file(argc, argv, u_coarse);     printf("%g\n", u_coarse->ultimatet); 

my struct is:

typedef struct {      double ultimatet; }utype; 

sorry, i've been trying not show since research.

your code has several problems

1. you never check if strtok() failed or not, can cause valgrind report reporting, or else since causes undefined behavior.

2. you use strlen() wrong, strlen() loops through string means in each iteration looping same number of times. must store value , use stored value, it's not more efficient, makes code prettier.

3. the loop never ends, because don't reassign end_of_file way worse name variable, should this

   while (current_line = fgets(buffer, sizeof(buffer), input_file)) ... 

4. you filling buffer array manually written loop when can use memset()

   memset(buffer, ' ', sizeof(buffer) - 1); buffer[sizeof(buffer) - 1] = '\0'; 

   would better job, syntactically , more efficient, , nul terminate buffer, didn't do.

5. you never check if fopen() succeded, lead undefined behavior too, must check every function call worked expected, of them return special values or set special variables indicate when problem happens, failing check errors makes code unstable , if boss fire you. don't take wrong, saying because if follow advice write more robust code, , have way less problems.

6. this

   for (i = 1 ; < strlen(lines_temp) ; i++)  {     lines_temp[i - 1] = lines_temp[i];  } lines_temp[strlen(lines_temp) - 2] = '\0'; 

   is bad several reasons

   1. you should not loop yourself, use memmove() instead.

      size_t length = strlen(lines_temp); memmove(lines_temp, lines_temp + 1, length); 

   2. if write loop yourself, efficient way be

      for (i = 1 ; lines_temp[i] != 0 ; i++)  {     lines_temp[i - 1] = lines_temp[i];  } lines_temp[i - 1] = '\0';