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5 1
ANSI C Solaris Unix UNIX
ls parameter ls parameter -l -la cp source-file destination-file
mv source-file destination-file
ls1.
Array Of Character ls,ls l,ls la exit
keyboard Input
data strcmp (String Compare) #include system#include strcmp 0
system ls ls
exit Not command found => ( command promt)
2. Input program screen
ls
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ls -l
ls -la
exit ( command promt solaris )
error
3. Output program screen
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4. Source Code
cp1. Cp copy
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2 char fopen r fopen w+ if while loop gets 49 50
puts fclose Copy Complete
2. Input program screen test.txt
copy cpmpile cp copy test.txt test2.txt
error
exit ls test2.txt copy
3. Output program screen
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4. Source Code
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mv
1. cp remove fclose(fp1) 1 1 if if = 0 move
cp2. Input program screen
test.txt test_folder /root/Desktop
move mv test.txt
Test_folder test2.txt
error
exit ls test.txt
test_folder
3.Output program screen
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4. Source Code
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21. Open and Read File
1. Use vi editor to key in the following program and save it to
afile read.c
#include #include
main(){int fd;ssize_t nread;char buf[1024];
/* open file "data" for reading */fd = open("data",
O_RDONLY);
if (fd == -1){
perror(Error in read data);exit(1);
}
/* read in the data */nread = read(fd, buf, 1024);printf(Number
of characters read: %d, nread);
/* close the file */close(fd);
}
2. Compile the program by typing: gcc read.c o read3. Run the
executable read4. Check the program output.
What is the output of the program?5. Use an editor to create a
file called data and type abcd1234in the file.6. Run the executable
read again7. Check the program output.
What is the output of the program?Why does it produce such
output?
21. code read.c2. gcc read.c o read3. exe
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4.
5. data abcd1234
6. read.exe 7. data char
8 9 \0 (Null Character)
2 . Creat and white a file2.1 vi source code write.c2.2 gcc
write.c o write
2.3 write.exe2.4
2.5
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2.6 wfile 2.7 ls l wfile 2.8 vi cat
2. Create and Write a file
1. Use vi editor to key in the following program and save it to
afile write.c
#include #include #include
#define PERMS 0644 /* permission for open with O_CREAT */
main(){
int fd;char *filename = "wfile";char *content = "Hello
World!";
fd = open(filename, O_WRONLY|O_CREAT, PERMS);
if (fd == -1){printf("Couldn't create %s\n", filename);exit(1);
/* error, so exit */
}
printf(Before writing string to file\n);
write(fd, content, strlen(content));printf(After writing string
to file\n);close(fd);
exit(0);}
2. Compile the program by typing: gcc write.c o write3. Run the
executable write4. Try to understand the flow of program
5. Check the program output.What is the output of the
program?
6. Look for a file wfile in the current directory.7. Use ls l
wfile to check the file permission of the file.
What is the file permission?Why it has such file permission?
8. Use vi to open it or use cat to list out the file content.
Whatis the file content?
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3. Standard input, standard output and standard error
A UNIX system automatically opens three files for any
executingprogram. These are standard input, standard output and
standarderror.
1. Use vi editor to key in the following program and save it to
afile io.c
/* Filename: io.c */#include #include
#define SIZE 512
main(){ssize_t nread;char buf[SIZE];
while( (nread = read(0, buf, SIZE)) > 0){
write(1, buf, nread);}exit(0);
}
2. Compile the program by typing: gcc io.c o io3. Run the
executable io4. Enter some text.5. Check the screen output.
What is the program doing?In system call read(0, buf, SIZE),
what does the first argument
0 means?In system call write(1, buf, nread), what does the
first
argument 1 means?
6. Press to exit the program. means endof input.4. Writing error
message with fprintfprintf can be used for displaying diagnostic
messages.Unfortunately, it writes to standard output, not standard
error.However, we can now use fprintf, a generalization of printf,
to do
this.
1. Use vi editor to modify read.c2. Replace the statement
perror(Error in read data); tofprintf(stderr, File data not
found\n);3. Save the modified source file to errorio.cThe program
should look like the following:
#include #include #include
#include
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main(){int fd;ssize_t nread;char buf[1024];
/* open file "data" for reading */fd = open("data",
O_RDONLY);
if (fd == -1){
fprintf(stderr, File data not found\n);
exit(1);}
/* read in the data */nread = read(fd, buf, 1024);printf(Number
of characters read: %d\n, nread);
/* close the file */close(fd);
}
4. Remove file data by entering: rm data.
5. Compile the program by typing: gcc errorio.c o errorio6. Run
the executable errorio
7. Check the screen output.What is the program output?What is
the difference between read.c and errorio.c?
Revision Exercise
Try to modify the read.c file to display file datas content
toscreen.
main( int argc, char **argv){.....}
argc parameter command-line() argv parameter
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argv[0] argv[1] parameter #1argv[2] parameter #2argv[3]
parameter #3
progname 37 15
argc = 3argv[0] = "progname"argv[1] = "37"argv[2] = "15"
2 . Creat and white a file2.1 vi source code write.c2.2 gcc
write.c o write
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2.3 write.exe
2.4 2.5
2.6 wfile 2.7 ls l wfile 2.8 vi cat
