c - Completing my own shell code -

i have created shell in c , here code.i have commented code.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/wait.h> #include <sys/types.h> #include <unistd.h> #include <signal.h>  #define path        "path="  //just constant string #define delim       ":"     //just constant string       typedef void (*sighandler_t)(int); char* cwdtemp = ""; int false=0;  /*structure of functions*/  char* readline(char* line, size_t len); void split(char* input, char *argv[]); int checkpipe( char *input); void run (char* argv[]); void runpipe(char *argv[], char *argv2[]); void setpath(char* inputline); char* getpath(); void changedir(char*  dir); char* strcasestr(const char *haystack, const char *needle); void handle_signal(int signo);    int main(){      char* input=null;  //string save user input     char* input2;       //string save 2nd command if theres pipe     char *argv[50];     //array sabe user input after spliting spaces     char *argv2[30];    //array save second command if thrs pipe     char argv3[100];    //array use of getcwd function     int i;              //varibale save index of pipe     char* cwd;          //variable save current working directory       while (1) {                     //infinite while loop           signal(sigint, sig_ign);        //capture teh signal , ignore default action         signal(sigint, handle_signal);  //capture signal , parse handle signal function          cwd=getcwd(argv3,100);      // current working directory , save cwd         cwdtemp=cwd;                //save current directory string cwdtemp         printf("%s",cwd);           //print cwd         printf(":~mosh:~$ ");       //show prompt              input=readline(input, 0);   //read user input , save string(char array)             if(strcasestr(input, path) == input){   //strcasesrt function check user input , see if has "path="(substring matching)             setpath(input);                     //pass user input setpath function                }else{               i=checkpipe(input);                 //saves index of ' | ' charactor in user input string              if(i==0){                           //if theres no  pipe                 split(input, argv);             //split user input spaces , save them in argv array                 if(argv[0] == null) {           //if user input null continue loop                     continue;                 }                    /* exit shell when "exit" inputed */                 if(strcmp(argv[0], "exit") == 0) {                                       exit(0);                 }                     if(strcmp(argv[0], "cd") == 0) {    //if user entered cd command(its not found in /bin)                                  changedir(argv[1]);             //pass name of directory should changed changedir function                  }                    run(argv);              //pass argv array run function                 /*checks if command valid*/                    if(false==-1 ){                     if(strcmp(argv[0], "exit") == 0){}                     else if(strcmp(argv[0], "cd") == 0){}                     else{                     printf("no such mosh command\n");}                      false=0;                     }             }               else{                       //if thers pipe                 input2=&input[i+1];     //points input2 memory location of charactor after charactor '|'                   input[i]='\0';          //adds escape charatctor charactor before '|' charactor of input , signal end of input string                 split(input, argv);     //split input spaces , save in argv array                   split(input2, argv2);   //split input2 spaces , save in argv2 array                  if(fork()){             //creates child process                     wait(null);         //wait till child process terminates                 }                  else{                       //else execute pipe in parent process                      runpipe(argv, argv2);                                }               }         }                    }    }  /*split input space , fill given array*/ void split(char* input, char *argv[]){     char* p;                   //char array     int argc;                        argc=0;                                      p=strtok(input, " ");       //torkanize user input spaces , save p        while(p!=null){         //until thrs charactors in p         argv[argc]=p;                    argc++;         p=strtok(null, " ");    //points torkanizer point stoped before , torkanize p     }        argv[argc]='\0';            //adds end of string last index of argv }  /* read line */ char* readline(char* line, size_t len){      getline(&line, &len, stdin);                 *(line+strlen(line)-1)='\0';     return line; }  /*return array index of | character if any, otherwise 0*/ int checkpipe( char *input){     int = 0;     int returnvalue = 0;     ( ; < strlen ( input ) ; i++ ){         if ( input[i] == '|' ){             //find index '|' in userinput , retuen index ,if not found return 0             returnvalue = i;             break;         }        }     return returnvalue; }  /*execute command without | in process*/ void run (char* argv[]){     pid_t pid = fork();     //creats fork , save pid in pid variable             if(pid == -1) {                                  perror("fork");         exit(1);     } else if(pid == 0) {               //if child process created         false=execvp(argv[0], argv);            //execute command execcvp function         //exit(0);     } else {                                 wait(null);                     //wait till child process terminates     }    }  /*execute command | in 2 processes*/ void runpipe(char *argv[], char *argv2[]){       int pfds[2];            //int array used in file descriptors      pipe(pfds);             //creates pipe     int stdin_bak = dup(0);      if (fork()==0) {            //if creation of fork successfull         close(1);               //close current stdout         dup(pfds[1]);           //duplicate stdout write end of pipe         close(pfds[0]);         //close stdin         printf("i'm child\n");         execvp(argv[0], argv);  //execute teh command         exit(0);     } else {                    //else in parent         close(0);               //close current stdin         dup(pfds[0]);           //duplicate stdin read end of pipe         close(pfds[1]);         //close stdout         wait(null);             //wait till child process terminates         execvp(argv2[0], argv2);//execute command                    } }  /*add given path environmental variable path*/ void setpath(char* inputline){       char* pathin = &inputline[strlen(path)];                    //save input path given user(without path=)     char* oldpath = getenv("path");                             //get current path getenv function , save oldpath     int lenpath = strlen(oldpath) + strlen(pathin) + 1 + 1;          char* pathout = malloc(sizeof(char) * lenpath);         //allocate memoery pathout malloc     strcat(pathout, oldpath);                                   //combine oldpath , pathout , save pathout strcat function     strcat(pathout, delim);                                     //combine oldpath , delim(constant string) , save pathout     strcat(pathout, pathin);                                    //combine oldpath , pathinand save pathout      pathout[lenpath - 1] = '\0';         setenv("path", pathout, 1);                                 //set new path setenv function     free(pathout);                                              //free memory allocated malloc    }  /*change directory if possible*/ void changedir(char* dir){     if(dir=='\0'){              //if user entered nothing after cd         chdir( "/home/" );      //change home     }else{         if(chdir(dir)==-1){     //if chdir function returned error               printf("%s:cannot find directory\n",dir);         }     } }    void handle_signal(int signo) {     printf("\n");     printf("%s",cwdtemp);     printf(":~mosh:~$ ");     fflush(stdout); //flush stdout or printf in sameline  } 

here problem. after compiling code have given command "hdgdg" wrong one.so output "command not found".but when run command "hakka|akjk"(which pipe command),i've got infinite loop output.so how can solve this? thank you.