#include < sys/uio.h > #include < stdio.h > int main() { ssize_t n; struct iovec vector[3]; vector[0].iov_base = "Hello"; vector[0].iov_len = 5; vector[1].iov_base = " "; vector[1].iov_len = 1; vector[2].iov_base = "World\n"; vector[2].iov_len = 6; if ((n = writev(1, vector, 3))< 0){ perror("writev"); return 1; } return 0; }
Month: June 2016
readv
長さが違う3個の読み込み用バッファを用意して、readvで読み込む。
#include < sys/uio.h > #include < stdio.h > int main() { int i; ssize_t n; char buf1[5], buf2[10], buf3[15]; struct iovec vector[3]; vector[0].iov_base = buf1; vector[0].iov_len = sizeof buf1; vector[1].iov_base = buf2; vector[1].iov_len = sizeof buf2; vector[2].iov_base = buf3; vector[2].iov_len = sizeof buf3; if ((n = readv(0,vector, 3)) < 0){ perror("readv"); return 1; } for (i = 0; i < 3; i++){ if (n < vector[i].iov_len){ vector[i].iov_len = n; } n -= vector[i].iov_len; printf("buf%d[] = %.*s\n", i, (int)vector[i].iov_len, (char *)vector[i].iov_base); } return 0; }
getdtablesize
#include#include int main(){ int s; s=getdtablesize(); printf("getdtablesize() = %d\n", s); return 0; }
fstatvfs
#include < sys/statvfs.h > #include < sys/types.h > #include < sys/stat.h > #include < fcntl.h > #include < stdio.h > int main() { int fd; struct statvfs buf; if((fd = open(".", O_RDONLY)) < 0){ perror("open"); return 1; } if (fstatvfs(fd, &buf) < 0){ perror("fstatvfs"); return 1; } printf( (sizeof(fsblkcnt_t) == 8) ?( "f_bsize = %lu, f_frsize = %lu,\n" "f_blocks = %llu, f_bfree = %llu, f_bavail = %llu, \n" "f_files = %llu, f_ffree = %llu, f_favail = %llu,\n" "f_fsid = %lx, f_flag= %lx, f_namemax = %lu\n" ) : ( "f_bsize = %lu, f_frsize = %lu,\n" "f_blocks = %llu, f_bfree = %lu, f_bavail = %lu, \n" "f_files = %lu, f_ffree = %lu, f_favail = %lu,\n" "f_fsid = %lx, f_flag= %lx, f_namemax = %lu\n" ), buf.f_bsize, buf.f_frsize, buf.f_blocks, buf.f_bfree, buf.f_bavail, buf.f_files, buf.f_ffree, buf.f_favail, buf.f_fsid, buf.f_flag, buf.f_namemax ); return 0; }
statvfs
カレントディレクトリが属するファイルシステムの情報取得
#include < sys/statvfs.h > #include < stdio.h > int main() { struct statvfs buf; if(statvfs(".", &buf) < 0){ perror("statvfs"); return 1; } printf( (sizeof(fsblkcnt_t)== 8)?( "f_bsize = %lu, f_frsize = %lu,\n" "f_blocks = %llu, f_bfree = %llu, f_bavail = %llu,\n" "f_files = %llu, f_ffree = %llu, f_favail = %llu,\n" "f_fsid = %lx, f_flag = %lx, f_namemax = %lu\n") : ( "f_bsize = %lu, f_frsize = %lu, \n" "f_blocks = %lu, f_bfree = %lu, f_bavail = %lu, \n" "f_fsid = %lx, f_flag = %lx, f_namemax = %lu\n"), buf.f_bsize, buf.f_frsize, buf.f_blocks, buf.f_bfree, buf.f_bavail, buf.f_files, buf.f_ffree, buf.f_favail, buf.f_fsid, buf.f_flag, buf.f_namemax); return 0; }
複数のファイル記述子を同時に監視
#include < sys/select.h > #include < stdio.h > int main(){ int n; fd_set readfds; struct timeval tv; FD_ZERO(&readfds); FD_SET(0, &readfds); FD_SET(4, &readfds); tv.tv_sec = 2; tv.tv_usec = 500000; n = select(5, &readfds, NULL, NULL, &tv); if (n < 0){ perror("select"); return 1; } else if (n == 0){ printf("time out \n"); } else { if (FD_ISSET(0, &readfds)){ printf("input from fd = 0\n"); } if (FD_ISSET(4, &readfds)){ printf("input from fd = 4\n"); } } return 0; }
utimes
#include < sys/time.h > #include < time.h > #include < stdio.h > int main(){ struct timeval times[2]; struct tm t; t.tm_sec = 7; t.tm_min = 14; t.tm_hour = 12; t.tm_mday = 19; t.tm_mon = 0; t.tm_year = 138; t.tm_isdst = 0; times[0].tv_sec = mktime(&t); times[0].tv_usec = 0; times[1] = times[0]; if (utimes("file.txt",times) < 0){ perror("utimes"); return 1; } return 0; }
utime
#include#include #include #include int main() { struct utimbuf buf; struct tm t; t.tm_sec = 7; t.tm_min = 14; t.tm_hour = 12; t.tm_mday = 19; t.tm_mon = 0; t.tm_year = 138; t.tm_isdst = 0; buf.actime =mktime(&t); buf.modtime = buf.actime; if (utime("file.txt", &buf) < 0){ perror("utime"); return 1; } return 0; }
lstat
#include < sys/types.h > #include < sys/stat.h > #include < unistd.h > #include < time.h > #include < stdio.h > int main() { struct stat buf; if(lstat("file.txt", &buf) < 0){ perror("lstat"); return 1; } printf("%s", ctime(&buf.st_mtime)); return 0; }
stat
#include < sys/types.h > #include < sys/stat.h > #include < unistd.h > #include#include int main(){ struct stat buf; if (stat("file.txt", &buf) < 0){ perror("stat"); return 1; } printf("%s", ctime(&buf.st_mtime)); return 0; }