1. EECE.2160 ECE Application Programming
Instructor:
Dr. Michael Geiger
Fall 2018
Lecture 32:
Finish PE3
File I/O

2. ECE Application Programming: Lecture 32
Lecture outline
Remaining key dates
W 12/5: Program 7 due
M 12/10: Program 6 regrades due
Th 12/13: last day of classes; Program 8 due
P8 deals with file I/O (lectures 32-33)
M 12/17: Exam 3, 3-6 PM (room TBD)
Will post course evals online; you’ll submit eval at exam
W 12/19: All code due by 12:00 PM (noon)
Program 9: Worth up to 4 points extra credit on final avg
Resubmission deadline for P7 & P8
Today’s class
Finish PE4 (search functions)
File I/O
6/30/2019
ECE Application Programming: Lecture 32

3. ECE Application Programming: Lecture 32
Review: PE3
Given header files, main program
Complete specified functions
For the Name structure
void printName(Name *n): Print the name pointed to by n, using format <first> <middle>. <last>
void readName(Name *n): Prompt for and read a first, middle, and last name, and store them in the structure pointed to by n
SINew functions on next slide
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ECE Application Programming: Lecture 32

4. Review: PE3 (continued)
Given header files, main program
Complete specified functions
Name functions on previous slide
For the SINew structure
void printStudent(SINew *s): Print information about the student pointed to by s
void readStudent(SINew *s): Prompt for and read information into the student pointed to by s
void printList(SINew list[], int n): Print the contents of an array list that contains n StudentInfo structures
int findByLName(SINew list[], int n, char lname[]): Search for the student with last name lname in the array list. Return the index of the structure containing that last name, or -1 if not found
int findByID(SINew list[], int n, unsigned int sID): Search for the student with ID # sID in the array list. Return the index of the structure containing that last name, or -1 if not found
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ECE Application Programming: Lecture 32

5. ECE Application Programming: Lecture 32
Name functions
void printName(Name *n) { printf("%s %c. %s\n", n->first, n->middle, n->last); } void readName(Name *n) { char junk; printf("Enter name: "); scanf("%s %c%c %s", n->first, &n->middle, &junk, n->last);
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ECE Application Programming: Lecture 32

6. Single SINew functions
void printStudent(SINew *s) { printName(&s->sname); printf("ID #%.8u\n", s->ID); printf("GPA: %.2lf\n", s->GPA); }
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ECE Application Programming: Lecture 32

7. Single SINew functions (cont.)
void readStudent(SINew *s) { readName(&s->sname); printf("Enter ID #: "); scanf("%u", &s->ID); printf("Enter GPA: "); scanf("%lf", &s->GPA); }
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ECE Application Programming: Lecture 32

8. ECE Application Programming: Lecture 32
printList()
void printList(SINew list[], int n) { int i; // Loop index for (i = 0; i < n; i++) { printStudent(&list[i]); printf("\n"); } }
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ECE Application Programming: Lecture 32

9. ECE Application Programming: Lecture 32
findByLName()
int findByLName(SINew list[], int n, char lname[]) { int i; // Loop index // Search for student with matching name // in list for (i = 0; i < n; i++) { if (strcmp(lname, list[i].sname.last) == 0) return i; } // If end of loop reached, student wasn’t // found return -1;
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ECE Application Programming: Lecture 32

10. ECE Application Programming: Lecture 32
findByID()
int findByID(SINew list[], int n,
unsigned int sID) {
int i; // Loop index
// Search for student with
// matching ID in list
for (i = 0; i < n; i++) {
if (sID == list[i].ID)
return i; }
// If end of loop reached, student wasn’t
// found
return -1;
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ECE Application Programming: Lecture 32

11. ECE Application Programming: Lecture 32
File information
Files commonly used for input/output
Interface uses FILE pointers
FILE type defined in <stdio.h>
Allows access to necessary file characteristics
File characteristics include:
Name—for example z:\Visual Studio 2010\Projects\fileio\fileio\myinput.txt
Read/write permission
Type (binary or ASCII text)
Access (security; single/multiple user)
Position in file
Programmer doesn’t have to account for this info
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ECE Application Programming: Lecture 32

12. Basic file I/O functions
Before reading/writing file, program must gain access to file
fopen() function used to open file
Returns FILE * if successful, NULL otherwise
When done with file, program should close it
fclose() function used to close file
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ECE Application Programming: Lecture 32

13. ECE Application Programming: Lecture 32
fopen()
FILE *fopen(char *fname, char *faccess)
fname: name of file (e.g., "f1.txt")
Name may require full path
faccess: string providing
First char: access mode
r/w/a (read/write/append)
Write starts at beginning of file, append starts at end
Either write or append creates new file if none exists
Additional (optional) char: file type
b/t (binary/text)
Text files are human readable (default--don’t need t)
Binary files are just raw bytes
Valid access strings: "r", "w", "a", "rb", "wb", "ab"
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ECE Application Programming: Lecture 32

14. ECE Application Programming: Lecture 32
fopen() (continued)
If successful, fopen() returns valid FILE * to be used with file read/write functions
If unsuccessful, fopen() returns NULL
Test this error condition to ensure file opened
Why might fopen() be unsuccessful?
Try to open input file that doesn’t exist
Try to open read-only file for writing
Try to open file that’s locked by another application
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ECE Application Programming: Lecture 32

15. ECE Application Programming: Lecture 32
fopen() example
FILE *fp; fp = fopen("in1.txt", "r"); if (fp == NULL) printf("Couldn’t open file\n"); else { … // FILE * is valid // Continue with program }
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ECE Application Programming: Lecture 32

16. File i/o function calls
fclose(FILE *file_handle)
Closes a file
Argument is address returned by fopen()
fclose(fp);
Recommended for input files
Required for output files
OS often doesn’t write last bit of file to disk until file is closed
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ECE Application Programming: Lecture 32

17. Example of basic file function usage
int main() { FILE *fp; // Open text file for reading fp = fopen("in.txt", "r"); if (fp == NULL) { printf("Error: could not open in.txt"); return 0; } ... // CODE TO EXECUTE IF FILE OPENS fclose(fp); // Close file when done
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ECE Application Programming: Lecture 32

18. File i/o function calls: formatted I/O
fprintf(file_handle, format_specifier, 0+ variables)
file_handle: address returned by fopen()
Other arguments are same as printf()
Example: fprintf(fp, "x = %d", x);
fscanf(file_handle, format_specifier, 0 or more variables)
Other arguments are same as scanf()
Example: fscanf(fp, "%d%d", &a, &b);
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ECE Application Programming: Lecture 32

19. ECE Application Programming: Lecture 32
Next time
Character and line I/O
Reminders: remaining key dates
W 12/5: Program 7 due
M 12/10: Program 6 regrades due
Th 12/13: last day of classes; Program 8 due
P8 deals with file I/O (lectures 32-33)
M 12/17: Exam 3, 3-6 PM (room TBD)
Will post course evals online; you’ll submit eval at exam
W 12/19: All code due by 12:00 PM (noon)
Program 9: Worth up to 4 points extra credit on final avg
Resubmission deadline for P7 & P8
6/30/2019
ECE Application Programming: Lecture 32