Contents. NOTICE & Programming Assignment #1. QnA about last exercise. File IO exercise

Transcription

1 File I/O Examples Prof. Jin-Soo TA - Dong-Yun Lee(dylee@csl.skku.edu) Computer Systems Laboratory Sungkyunkwan University

2 Contents NOTICE & Programming Assignment #1 QnA about last exercise File IO exercise 2

3 Notice We will use sys server for assignment Both source code and report You can directly check your score via server You can change the final version of your code Be careful that your final version is right version There should be some restriction at server Maximum number of upload? etc 3

4 Programming Assignment #1 Let s check together PA #1 Some news.. 1. Input filename is *.txt (bible name is without.txt ) ex) genesis.txt, daniel.txt, etc.. 2. GNU make tools Your code should be compiled with the following cmd. $ make all 3. IndexPrinter : print the word with lowercase ex) the (O) The (X) 4

5 Report Report format : [ 학번 ].pdf I like simple, neat, clean, graphical, understandable, easy, and short report About your own data structure and functions 5

6 QnA For PA #1 6

7 Exercise Review (1) const qualifier void foo1(const char *s1) { s1[0] = a ; } void foo2(const char *s1) { s1 = hey ; } void foo3(const char *s1) { char *s = s1; } void foo4(const char *s1) { char *s = s1; s[0] = e ; } void foo5 (char * const s1) { s1[0] = a ; } void foo6(char * const s1) { s1 = hey ; } 7

8 Exercise Review (2) 8

9 Exercise Review (3) Why below code do not work correctly? Explain it correctly You can use anything for the answer int main(void) { char c; } while(read(0, &c, 1)!= 0) write(1, &c, 1); exit(0); 9

10 Remind 6 System calls open() close() read() write() lseek() stat() / fstat() 10

11 Example #1 (1) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 0 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \r \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 11

12 Example #1 (2) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); // "Hello." read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 6 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \r \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 12

13 Example #1 (3) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); // "Hello.\r\n" File state (FD: 3) path: "hello-dos.txt" position: 8 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \r \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 13

14 Example #1 (4) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 6 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \r \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 14

15 Example #1 (5) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 7 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \n \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 15

16 Example #1 (6) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 8 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \n \n W h o a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 16

17 Example #1 (7) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); File state (FD: 3) path: "hello-dos.txt" position: 11 size: 20 lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); H e l l o. \n \n H o w a r e y o u? EOF fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 17

18 Example #1 (8) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; File state (FD: 3) :CLOSED fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 18

19 Example #1 (9) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; // long long; fd = open(filename, O_RDWR O_CREAT, 0755); read(fd, buffer, 6); read(fd, buffer+6, 2); lseek(fd, -2, SEEK_CUR); buffer[0] = '\n'; write(fd, buffer, 1); lseek(fd, 8, SEEK_SET); strcpy(buffer, "How"); write(fd, buffer, 3); close(fd); fd = open(filename, O_WRONLY O_CREAT O_EXCL, 0755); if (fd < 0) printf("errno : %d, error code - EEXIST : %d\n", errno, EEXIST); 19

20 Example #2 (1) File state (FD: 3) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; fd = open(filename, O_WRONLY); lseek(fd, 1, SEEK_END); strcpy(buffer, "!\n"); write(fd, buffer, 2); close(fd); path: "hello-dos.txt" type: Regular mode: Write only position: 0 size: 20 H e l l o. \r \n W h o a r e y o u? EOF 20

21 Example #2 (2) File state (FD: 3) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; fd = open(filename, O_WRONLY); lseek(fd, 1, SEEK_END); strcpy(buffer, "!\n"); write(fd, buffer, 2); close(fd); path: "hello-dos.txt" type: Regular mode: Write only position: 21 size: 20 H e l l o. \r \n W h o a r e y o u? EOF 21

22 Example #2 (3) File state (FD: 3) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; fd = open(filename, O_WRONLY); lseek(fd, 1, SEEK_END); strcpy(buffer, "!\n"); write(fd, buffer, 2); close(fd); path: "hello-dos.txt" type: Regular mode: Write only position: 23 size: 23 H e l l o. \r \n W h o a r e y o u? \0! \n EOF Data hole 22

23 Example #2 (4) char filename[] = "hello-dos.txt"; int fd; char buffer[16]; off_t pos = 0; File state (FD: 3) :CLOSED fd = open(filename, O_WRONLY); lseek(fd, 1, SEEK_END); strcpy(buffer, "!\n"); write(fd, buffer, 2); close(fd); 23

24 File Metadata Data about data, in this case file data. Maintained by kernel, accessed by users with the stat and fstat functions. /* Metadata returned by the stat and fstat functions */ struct stat { dev_t st_dev; /* device */ ino_t st_ino; /* inode */ mode_t st_mode; /* protection and file type */ nlink_t st_nlink; /* number of hard links */ uid_t st_uid; /* user ID of owner */ gid_t st_gid; /* group ID of owner */ dev_t st_rdev; /* device type (if inode device) */ off_t st_size; /* total size, in bytes */ unsigned long st_blksize; /* blocksize for filesystem I/O */ unsigned long st_blocks; /* number of blocks allocated */ time_t st_atime; /* time of last file access */ time_t st_mtime; /* time of last file modification */ time_t st_ctime; /* time of last inode change */ }; /* statbuf.h included by sys/stat.h */ 24

25 Accessing File Metadata /* statcheck.c - Querying and manipulating a file s meta data */ int main (int argc, char **argv) { struct stat st; char *type, *readok; stat(argv[1], &st); if (S_ISREG(st.st_mode)) /* file type */ type = "regular"; else if (S_ISDIR(st.st_mode)) type = "directory"; else type = "other"; if ((st.st_mode & S_IRUSR)) /* OK to read? */ readok = "yes"; else readok = "no"; bass>./statcheck statcheck.c type: regular, read: yes bass> chmod 000 statcheck.c bass>./statcheck statcheck.c type: regular, read: no } printf("type: %s, read: %s\n", type, readok); exit(0); 25

26 Lab 2. Exercise (1) Make the following program Unix Dos Newline <LF> <CR> <LF> <TAB> char 8 consecutive <space> -> <TAB> <TAB> -> 4 consecutive <space> If input file is Unix format, convert it to the dosformat If input file is Dos format, convert it to the Unixformat 26

27 Lab 2. Exercise (2) Make the following program Unix Dos Newline <LF> <CR> <LF> <TAB> char 8 consecutive <space> -> <TAB> <TAB> -> 4 consecutive <space> 27

28 Lab 2. Exercise (3) Make the following program Unix Dos Newline <LF> <CR> <LF> <TAB> char 8 consecutive <space> -> <TAB> <TAB> -> 4 consecutive <space>./convert [input_file] You should name the output file as [input_file].out You cannot use fopen, fread, fwrite and fclose Instead, use open, read, write and close Test file is uploaded at project page 28