我尝试在代码的不同位置上投射（char *），但没有任何帮助...... 我也有以下错误：
OSCourseProject1.c: In function ‘main’:
OSCourseProject1.c:18:21: warning: assignment makes integer from pointer without a cast [enabled by default]
singleUserCommand = strtok(tempUserCommands," ");
^
OSCourseProject1.c:19:29: warning: comparison between pointer and integer [enabled by default]
while ( singleUserCommand != NULL )
^
OSCourseProject1.c:21:4: warning: passing argument 1 of ‘strcmp’ makes pointer from integer without a cast [enabled by default]
if ( strcmp( singleUserCommand, "leave") != 0 )
^
In file included from OSCourseProject1.c:2:0:
/usr/include/string.h:144:12: note: expected ‘const char *’ but argument is of type ‘char’
extern int strcmp (const char *__s1, const char *__s2)
^
OSCourseProject1.c:25:5: warning: passing argument 2 of ‘strcmp’ makes pointer from integer without a cast [enabled by default]
while ( strcmp(tempShellPath, singleUserCommand)==0 &&
^
In file included from OSCourseProject1.c:2:0:
/usr/include/string.h:144:12: note: expected ‘const char *’ but argument is of type ‘char’
extern int strcmp (const char *__s1, const char *__s2)
^
OSCourseProject1.c:33:8: warning: format ‘%s’ expects argument of type ‘char *’, but argument 2 has type ‘int’ [-Wformat=]
singleUserCommand);
^
OSCourseProject1.c:45:24: warning: assignment makes integer from pointer without a cast [enabled by default]
singleUserCommand = (char*)strtok(NULL, " ");
^
/tmp/ccAuy2Eg.o: In function `main':
OSCourseProject1.c:(.text+0x11): undefined reference to `getnv'
collect2: error: ld returned 1 exit status
这是我写的代码（我应该从用户那里收到一行命令 按命令分解它们并分别运行每个命令。
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
main ()
{
char * shellPath = (char *)getnv("PATH");
char * tempShellPath, singleUserCommand;
char * singleShellCommand;
char * userCommands = (char*)malloc(100);
char * tempUserCommands = (char*)malloc(100);
int forker, runOrDie = 1;
while (runOrDie)
{
printf("<Please enter a command>");
fgets(userCommands, 100, stdin);
strcpy(tempUserCommands, userCommands);
singleUserCommand = strtok(tempUserCommands," ");
while ( singleUserCommand != NULL )
{
if ( strcmp( singleUserCommand, "leave") != 0 )
{
strcpy( (char*)tempShellPath, (char*)shellPath);
singleShellCommand = (char*)strtok(tempShellPath, ":");
while ( strcmp(tempShellPath, singleUserCommand)==0 &&
singleShellCommand != NULL )
{
singleShellCommand = strtok(NULL, ":");
}
if ( singleShellCommand == NULL)
{
printf("%s - no such command exists!",
singleUserCommand);
}
else
{
if ( (forker = fork()) == 0 )
{
execv(singleShellCommand, singleUserCommand);
}
else
{
wait( &forker );
}
singleUserCommand = (char*)strtok(NULL, " ");
}
}
else
{
runOrDie = 0;
}
}
}
}
答案 0 :(得分：3)
char * tempShellPath, singleUserCommand;
这将是
char *tempShellPath;
char singleUserCommand;
您需要的是：
char *singleUserCommand;
答案 1 :(得分：0)
rather than trying to list all the problems via comments.
(your original code yielded some 60 errors/warnings)
the following code will compile with no errors/warnings
Do read the notes in the file (most notes contain '<--'
Do notice the error checking
Do notice the new function cleanUp() to assure no memory leaks
Do notice that second parameter in call to execv() still needs fixing
always place literal on left when performing a comparison
so compiler catches '=' .vs. '==' errors
use meaningful names
use proper return value typing and error checking
// <-- added missing header files
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h> // pid_t definition
#include <sys/types.h>
#include <sys/wait.h> // wait() prototype
#define MAX_USER_COMMANDS_LEN (100) // <-- so changing size easy and no magic number in code
// pointers here so visible to cleanUp and main
char * shellPath = NULL;
char * tempShellPath = NULL;
char * userCommands = NULL;
char * tempUserCommands = NULL;
char * singleUserCommand = NULL;
char * singleShellCommand = NULL;
// prototypes
void cleanUp( void ); // <-- new function
int main () // <-- corrected
{
pid_t childPid; // <-- corrected
int pidStatus; // status set by wait() // <-- corrected
if( NULL == (shellPath = getenv("PATH")) ) // <-- added error checking
{ // then getenv failed
perror( "getenv failed for PATH" );
cleanUp();
exit( EXIT_FAILURE );
}
// implied else, getenv successful
if( NULL == (userCommands = malloc(MAX_USER_COMMANDS_LEN)) ) // <-- added error checking
{ // then, malloc failed
perror( "malloc failed for userCommands" );
cleanUp();
exit( EXIT_FAILURE );
}
// implied else, malloc successful
if( NULL == (tempShellPath = malloc( strlen(shellPath) +1) ) ) // added error checking
{ // then malloc failed
perror( "malloc failed for tempShellPath" );
cleanUp();
exit( EXIT_FAILURE );
}
// implied else, malloc successful
while (1)
{
printf("<Please enter a command>");
if( NULL == fgets(userCommands, 100, stdin) ) // <-- added error checking
{ // then fgets failed
perror( "fgets failed for userCommands" );
cleanUp();
exit( EXIT_FAILURE );
}
// implied else, fgets successful
if( NULL == (tempUserCommands = malloc( strlen( userCommands )+1) ) ) // <-- added error checking
{ // then malloc failed
perror( "malloc failed" );
cleanUp();
exit( EXIT_FAILURE );
}
// implied else, malloc successful
strcpy(tempUserCommands, userCommands);
singleUserCommand = strtok(tempUserCommands," ");
while ( NULL != singleUserCommand )
{
// note: suggest: 'quit' or 'q' as intuitive rather than 'leave'
if ( 0 == strcmp( singleUserCommand, "leave") ) break; // exit while loop
// +++++++++++++++++++++++++++++++++++++++++++++++++
// replace following with something reasonable
// perhaps a 'whereis' kind of call
// note: shellPath is a series of directory paths, not executables separated by ':'
//
// strcpy( tempShellPath, shellPath);
// singleShellCommand = (char*)strtok(tempShellPath, ":");
// while (
// ( strcmp(tempShellPath, singleUserCommand)==0)
// &&
// (singleShellCommand != NULL) )
// {
// singleShellCommand = strtok(NULL, ":");
// }
//
// if ( singleShellCommand == NULL)
// {
// printf(" - no command entered!\n");
// }
//
// else
// {
if ( 0 == (childPid = fork()) )
{ // then child
// ERROR: singleUserCommand(in the following line)
// must be an array of pointers to strings,
// with a final pointer of NULL
if( -1 == execv(singleShellCommand, (char * const*)singleUserCommand) )
{ // command failed // <-- added error checking
perror( "execv failed" );
cleanUp(); // test to assure this is 'ok' to use here
exit( EXIT_FAILURE ); // execv should never return
}
}
else
{ // else parent
wait( &pidStatus ); // wait for only child to complete
} // end if
singleUserCommand = strtok(NULL, " ");
// } // end if
} // end while
free( tempUserCommands ); tempUserCommands = NULL; // <-- prep for next pass through loop
} // end while
cleanUp(); // < -- added free of malloc'd areas
return(0); // <-- added proper return statement
} // end function: main
// <-- added following function to assure no memory leaks
void cleanUp()
{
free( tempShellPath ); tempShellPath = NULL;
free( userCommands ); userCommands = NULL;
free( tempUserCommands ); tempUserCommands = NULL;
} // end function: cleanUp