いつかまとめる予定②

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とりあえずpsコマンドのソース

minimal.c

#ifdef __linux__
/* return 1 if it works, or 0 for failure */
static int stat2proc(int pid) {
char buf[800]; /* about 40 fields, 64-bit decimal is about 20 chars */
int num;
int fd;
char* tmp;
struct stat sb; /* stat() used to get EUID */
snprintf(buf, 32, "/proc/%d/stat", pid);
if ( (fd = open(buf, O_RDONLY, 0) ) == -1 ) return 0;
num = read(fd, buf, sizeof buf - 1);
fstat(fd, &sb);
P_euid = sb.st_uid;
close(fd);
if(num<80) return 0;
buf[num] = '\0';
tmp = strrchr(buf, ')'); /* split into "PID (cmd" and "<rest>" */
*tmp = '\0'; /* replace trailing ')' with NUL */
/* parse these two strings separately, skipping the leading "(". */
memset(P_cmd, 0, sizeof P_cmd); /* clear */
sscanf(buf, "%d (%15c", &P_pid, P_cmd); /* comm[16] in kernel */
num = sscanf(tmp + 2, /* skip space after ')' too */
"%c "
"%d %d %d %d %d "
"%lu %lu %lu %lu %lu %lu %lu "
"%ld %ld %ld %ld %ld %ld "
"%lu %lu "
"%ld "
"%lu %lu %lu %lu %lu %lu "
"%u %u %u %u " /* no use for RT signals */
"%lu %lu %lu",
&P_state,
&P_ppid, &P_pgrp, &P_session, &P_tty_num, &P_tpgid,
&P_flags, &P_min_flt, &P_cmin_flt, &P_maj_flt, &P_cmaj_flt, &P_utime, &P_stime,
&P_cutime, &P_cstime, &P_priority, &P_nice, &P_timeout, &P_alarm,
&P_start_time, &P_vsize,
&P_rss,
&P_rss_rlim, &P_start_code, &P_end_code, &P_start_stack, &P_kstk_esp, &P_kstk_eip,
&P_signal, &P_blocked, &P_sigignore, &P_sigcatch,
&P_wchan, &P_nswap, &P_cnswap
);
/* fprintf(stderr, "stat2proc converted %d fields.\n",num); */
P_vsize /= 1024;
P_rss *= (PAGE_SIZE/1024);

memcpy(P_tty_text, " ? ", 8);
if (P_tty_num != NO_TTY_VALUE) {
int tty_maj = (P_tty_num>>8)&0xfff;
int tty_min = (P_tty_num&0xff) | ((P_tty_num>>12)&0xfff00);
snprintf(P_tty_text, sizeof P_tty_text, "%3d,%-3d", tty_maj, tty_min);
}

if(num < 30) return 0;
if(P_pid != pid) return 0;
return 1;