Posix file operations c

If a file is removed from or added to the directory hierarchy being searched it is unspecified whether or not find includes that file in its search.

The following options shall be supported by the implementation: -H Cause the file information and file type evaluated for each symbolic link encountered as a path operand on the command line to be those of the file referenced by the link, and not the link itself.

If the referenced file does not exist, the file information and type shall be for the link itself. File information and type for symbolic links encountered during the traversal of a file hierarchy shall be that of the link itself. Specifying more than one of the mutually-exclusive options -H and -L shall not be considered an error.

The last option specified shall determine the behavior of the utility. If neither the -H nor the -L option is specified, then the file information and type for symbolic links encountered as a path operand on the command line or encountered during the traversal of a file hierarchy shall be that of the link itself.

OPERANDS The following operands shall be supported: The first operand and subsequent operands up to but not including the first operand that starts with a '-', or is a '!

If the first operand starts with a '-', or is a '! Each path operand is a pathname of a starting point in the file hierarchy.

The first operand that starts with a '-', or is a '! The following primaries shall be supported: -name pattern The primary shall evaluate as true if the basename of the current pathname matches pattern using the pattern matching notation described in Section 2. The additional rules in Section 2. If any -xdev primary is specified, it shall apply to the entire expression even if the -xdev primary would not normally be evaluated. If the -depth primary is specified, the -prune primary shall have no effect.

To start, a template shall be assumed with all file mode bits cleared. Since the initial mode is all bits off, there are not any symbolic modes that need to use '-' as the first character. In both cases, the behavior is unspecified when onum exceeds If uname is a decimal integer and the getpwnam or equivalent function does not return a valid user name, uname shall be interpreted as a user ID.

If gname is a decimal integer and the getgrnam or equivalent function does not return a valid group name, gname shall be interpreted as a group ID.

If n is followed by the character 'c', the size shall be in bytes. Each invocation shall begin after the last pathname in the set is aggregated, and shall be completed before the find utility exits and before the first pathname in the next set if any is aggregated for this primary, but it is otherwise unspeci- fied whether the invocation occurs before, during, or after the evaluations of other primaries.

If any invocation returns a non- zero value as exit status, the find utility shall return a non-zero exit status. If the response on standard input is affirmative, the utility shall be invoked. Otherwise, the command shall not be invoked and the value of the -ok operand shall be false.

If a -depth primary is not specified, all entries in a directory shall be acted on after the directory itself. If any -depth primary is specified, it shall apply to the entire expression even if the -depth primary would not normally be evaluated.

The primaries can be combined using the following operators in order of decreasing precedence : expression True if expression is true.

Post by zliudr » Mon Jan 20, pm. Post by PeterR » Mon Jan 20, pm. Post by zliudr » Mon Feb 10, am. Post by PeterR » Mon Feb 10, pm. Post by zliudr » Thu Mar 05, pm. Post by PeterR » Sat Mar 07, am.

Post by zliudr » Sun Mar 08, pm. Post by PeterR » Mon Mar 09, am. Espressif Systems is a fabless semiconductor company providing cutting-edge low power WiFi SoCs and wireless solutions for wireless communications and Internet of Things applications.

Skip to content. POSIX file operations implemented on ESP32 Post by zliudr » Fri Jan 17, am Question: if one task does something such as rename files in a directory move them out of the directory , and another task does something else such as creating and writing files to the same folder, will there be any conflict?

Simple, quick, no more than a few 10's of nS performance hit etc. I just read about mutex seen the term but never investigated. It seems that I should write a function that accesses the file directory and have mutex in it. Then different tasks shall call the same function when they want access to file directories, such as creating a file, moving a file. If such thing as mutex already exists, why would a file operation library not do it internally to rid developers from having to do the same at application dev.

Just curious. There is a place where DOS stores a status that says it's running. It should be implemented below the app. Lots of documentation for the filesystem man.

Guess he might just say that you should marshal access to the file system, his life is too short. Maybe the former for simplicity and memory saving? In case of the single mutex for file system, I can just insert mutexTake right before any file operation and mutexGive right after.

I'm not sure if file content is buffered beyond fclose and hope not. If you are working with large files, allocating memory for the whole of file may not be a good idea at all. You may like to consider using memory mapped files for large files. POSIX systems provide mmap and munmap functions for mapping files or devices in memory. See mmap man page for more description. Memory mapped files work similar to C arrays though the responsibility of getting actual file data is left to the OS which fetches appropriate pages from disk as and when required while working on the file.

Memory mapped files approach has limitations if the file size is bigger than bit address space. Then you can map only part of a file at a time on bit machines. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

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