Get name from PID?

Question

I am on OSX Mountain Lion and am trying to retrieve a processes' name using its PID.

The following is the code I am using:

pid_t pid = 10687;
char pathBuffer [PROC_PIDPATHINFO_MAXSIZE] = "";
char nameBuffer [256] = "";

int sizeOfVal = sizeof(nameBuffer);
proc_pidpath(pid, pathBuffer, sizeof(pathBuffer));
proc_name(pid, nameBuffer, sizeof(nameBuffer));

NSLog(@"Path: %s\n Name: %s\n", pathBuffer, nameBuffer);

The code above is able to retrieve the name properly, however it only retrieves the first 15 characters and "ignores" the rest. Note this is not a problem with displaying the name, but with retrieving it. The problem is not with the rest of my application as I am testing the above code in a standalone application. Also note that I tried changing the PID, but regardless of what PID I try the code only retrieves the first 15 characters of the name. Path retrieval works perfectly.

Does anyone have any ideas about what I am doing wrong?

Answer 1

The function looks at the value is the struct proc_bsdshortinfo. It is limited to return a 16 byte string, or 15 readable characters when including the null terminator.

From sys/param.h:

#define MAXCOMLEN   16      /* max command name remembered */

From sys/proc_info.h:

struct proc_bsdshortinfo {
        uint32_t                pbsi_pid;       /* process id */
        uint32_t                pbsi_ppid;      /* process parent id */
        uint32_t                pbsi_pgid;      /* process perp id */
    uint32_t                pbsi_status;        /* p_stat value, SZOMB, SRUN, etc */
    char                    pbsi_comm[MAXCOMLEN];   /* upto 16 characters of process name */
    uint32_t                pbsi_flags;              /* 64bit; emulated etc */
        uid_t                   pbsi_uid;       /* current uid on process */
        gid_t                   pbsi_gid;       /* current gid on process */
        uid_t                   pbsi_ruid;      /* current ruid on process */
        gid_t                   pbsi_rgid;      /* current tgid on process */
        uid_t                   pbsi_svuid;     /* current svuid on process */
        gid_t                   pbsi_svgid;     /* current svgid on process */
        uint32_t                pbsi_rfu;       /* reserved for future use*/
};

EDIT: To get around this, get the last path component:

pid_t pid = 3051;
char pathBuffer [PROC_PIDPATHINFO_MAXSIZE];
proc_pidpath(pid, pathBuffer, sizeof(pathBuffer));

char nameBuffer[256];

int position = strlen(pathBuffer);
while(position >= 0 && pathBuffer[position] != '/')
{
    position--;
}

strcpy(nameBuffer, pathBuffer + position + 1);

printf("path: %s\n\nname:%s\n\n", pathBuffer, nameBuffer);