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Questions and Answers
What system call is used to create a file?
What system call is used to create a file?
What flags are used to create a new file and ensure that it can only be written to?
What flags are used to create a new file and ensure that it can only be written to?
What does the O_TRUNC flag do when used with the open() system call?
What does the O_TRUNC flag do when used with the open() system call?
What does the example code 'int fd = open("foo", O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR);' do?
What does the example code 'int fd = open("foo", O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR);' do?
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What does the third parameter of the open() system call specify?
What does the third parameter of the open() system call specify?
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Study Notes
File Creation System Calls
- The
open()system call is utilized for creating files in a Unix-like operating system.
Flags for Creating a File
-
O_CREATflag is used withopen()to create a new file if it does not already exist. -
O_WRONLYflag allows the file to be opened for writing only, restricting read access. - To ensure a file is writable exclusively, combining
O_CREATandO_WRONLYis essential.
O_TRUNC Flag Functionality
- The
O_TRUNCflag, when used withopen(), truncates an existing file to zero length upon opening, effectively deleting its contents.
Example Code Explanation
- The code
int fd = open("foo", O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR);creates a new file named "foo". - If "foo" already exists, its contents will be truncated due to the
O_TRUNCflag. - The file is created with permissions allowing the owner to read and write (
S_IRUSRandS_IWUSR).
Third Parameter of open() System Call
- The third parameter, typically the mode, specifies the file permissions when a new file is created.
- It dictates the access rights for the file owner, group, and others, in this case allowing read and write for the user only.
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Description
Quiz: File Creation in C Programming Test your knowledge of file creation in C programming with this quiz. Learn about using the open system call, file flags, and permissions to create new files in a C program.
