Does the argument list pass the string quotes to exec command in C?

问题:

I am using execvp for execing a new process for the command grep -l night *. Here is my code:

char * argument[5]; char keyword[] = "night";  argument[0] = (char *) malloc (sizeof(char)*25); argument[1] = (char *) malloc (sizeof(char)*25); argument[2] = (char *) malloc (sizeof(char)*25); argument[3] = (char *) malloc (sizeof(char)*25); argument[4] = (char *) malloc (sizeof(char)*25);  argument[0] = "grep"; argument[1] = "-l"; strcpy(argument[2],keyword); argument[3] = "*"; argument[4] = NULL;  execvp ("grep", argument);

But I am getting the output from this program as "grep: *: No such file or directory" which is incorrect as executing the same command from the shell results in the list of files which contain the text "night". I do suspect that the * in the command list is being sent as a string with quotes to exec. Is my assumption correct? If so how can I rectify this problem? Any help would be highly appreciated.

回答1:

Grep does not understand the "*" argument. Usually the shell expands such arguments (it's called globbing). Of course, since exec functions don't start a shell, you don't get that functionality.

You can:

• Use functions which do start a shell (system(3), popen(3))
• Use glob(3), essentially doing the shells job

EDIT

You could probably write it as this (untested):

glob_t globbuf; globbuf.gl_offs = 3;  /* Globbing magic. */ glob("*", GLOB_DOOFFS, NULL, &globbuf);  /* That's what the 3 was for. */ globbuf.gl_pathv[0] = "grep"; globbuf.gl_pathv[1] = "-l"; globbuf.gl_pathv[2] = "night";  /* Conveniently, the list is NULL-terminated. */ execvp("grep", globbuf.gl_pathv);

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