How to use execvp

Question

The user will read a line and i will retain the first word as a command for execvp    Lets say he will type  cat file txt      command will be cat   But i am not sure how to use this execvp    i read some tutorials but still didn t get it    include  lt stdio h gt   include  lt stdlib h gt   int main         char  buf      char command 32       char name 32       char  pointer      char line 80       printf   gt          while  buf   readline       NULL              if  strcmp buf  exit    0          break           if buf 0   NULL          add history buf            pointer   strtok buf                if pointer    NULL               strcpy command  pointer                      pid t pid           int  status           if   pid   fork     lt  0                     printf      ERROR  forking child process failed n                exit 1                     else if  pid    0                          if  execvp command  buf   lt  0                         printf      ERROR  exec failed n                    exit 1                                   else                                           while  wait  amp status     pid                               free buf           printf   gt             end While     return 0

User · Accepted Answer

The first argument is the file you wish to execute, and the second argument is an array of null-terminated strings that represent the appropriate arguments to the file as specified in the man page.

For example:

char *cmd = "ls";
char *argv[3];
argv[0] = "ls";
argv[1] = "-la";
argv[2] = NULL;

execvp(cmd, argv); //This will run "ls -la" as if it were a command

User · Answer

In cpp  you need to pay special attention to string types when using execvp   include  lt iostream gt   include  lt string gt   include  lt cstring gt   include  lt stdio h gt   include  lt unistd h gt  using namespace std   const size t MAX ARGC   15     1 command     of arguments char  argv MAX ARGC   1      Needs  1 because of the null terminator at the end    c str   converts string to const char   strdup converts const char  to char  argv 0    strdup command c str         start filling up the arguments after the first command size t arg i   1  while  cin  amp  amp  arg i  lt  MAX ARGC        string arg      cin  gt  gt  arg      if  arg empty              argv arg i    nullptr          break        else           argv arg i    strdup arg c str                 arg i        Run the command with arguments if  execvp command c str    argv     -1           Print error if command not found     cerr  lt  lt   quot command   quot   lt  lt  command  lt  lt   quot   not found n quot      Reference  execlp execvp

[c] How to use execvp()

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