file-descriptor

Is there any portable way (on POSIX systems) to determine if a file descriptor is seekable? My thought is to use lseek(fd, 0, SEEK_CUR); and check if the return value is -1, but I'm uncertain if this could give false negatives or false positives. Using fstat and making assumptions about what types of files are seekable/nonseekable does not sound like a good idea. Any other ideas? The lseek method seems reasonable. It certainly can't cause a false negative - if it did, something is seriously wrong with the implementation. Also, according to the POSIX spec , it is supposed to fail if the

I am interested to know the valid values which I can expect for a file descriptor. Please let me explain a bit. I know that, for instance, when I use #include <unistd.h> on my linux system then a call to open a file for reading: int fileDescriptor; fileDescriptor = open("/some/filename",O_RDONLY); an error might occur and I receive -1 as a result. Incidently the (-1) negative one must have somewhat of a special meaning. Is it that all other values are valid file descriptors? i.e. also negative ones like -2 and -1023? Assuming that int is 4 bytes ( sizeof(int)==4 ), then would (-1) = 10000000

Is HANDLE similar to file descriptor in Linux? As far as I know, HANDLE is used for handling every resources on Windows, such as font, icons, files, devices..., which in essence is just a void pointer point to a memory block holding data of a specific resource Yes, Windows handles are very similar to Unix file descriptors (FDs). Note that a HANDLE is not a pointer to a block of memory. Although HANDLE is typedef 'd as void * , that's just to make it more opaque. In practice, a HANDLE is an index that is looked up in a table, just as an FD number is. This blog post explores some of the

I'm creating a shell in C, and I need help implementing input and output redirection. When I try to create a file using ">" I get an error message saying the file does not exist. When I try to do something like ls > test.txt; it won't create a new file. I updated the code with the suggestions provided to me, but now I got different errors. However, a new file is still not created for the output redirection. This is my full code: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <unistd.h> #include <errno.h> #include <fcntl.h> #define MAX_BUF 160 #define MAX

I would like to know how many file descriptors have I opened in my C++ application. Can this be done using Windows API function? You can ask each handle in the process using GetFileType . DWORD type_char = 0, type_disk = 0, type_pipe = 0, type_remote = 0, type_unknown = 0, handles_count = 0; GetProcessHandleCount(GetCurrentProcess(), &handles_count); handles_count *= 4; for (DWORD handle = 0x4; handle < handles_count; handle += 4) { switch (GetFileType((HANDLE)handle)){ case FILE_TYPE_CHAR: type_char++; break; case FILE_TYPE_DISK: type_disk++; break; case FILE_TYPE_PIPE: type_pipe++; break;