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- From: Felix Fietkau <[email protected]>
- Date: Wed, 8 Oct 2025 22:15:42 +0200
- Subject: [PATCH] fs: add dup2() function
- Add dup2() function to duplicate file descriptors, useful for redirecting
- standard streams in child processes.
- Signed-off-by: Felix Fietkau <[email protected]>
- ---
- --- a/lib/fs.c
- +++ b/lib/fs.c
- @@ -1278,6 +1278,54 @@ uc_fs_fdopen(uc_vm_t *vm, size_t nargs)
- return ucv_resource_create(vm, "fs.file", fp);
- }
-
- +/**
- + * Duplicates a file descriptor.
- + *
- + * This function duplicates the file descriptor `oldfd` to `newfd`. If `newfd`
- + * was previously open, it is silently closed before being reused.
- + *
- + * Returns `true` on success.
- + * Returns `null` on error.
- + *
- + * @function module:fs#dup2
- + *
- + * @param {number} oldfd
- + * The file descriptor to duplicate.
- + *
- + * @param {number} newfd
- + * The file descriptor number to duplicate to.
- + *
- + * @returns {?boolean}
- + *
- + * @example
- + * // Redirect stderr to a log file
- + * const logfile = open('/tmp/error.log', 'w');
- + * dup2(logfile.fileno(), 2);
- + * logfile.close();
- + */
- +static uc_value_t *
- +uc_fs_dup2(uc_vm_t *vm, size_t nargs)
- +{
- + uc_value_t *oldfd_arg = uc_fn_arg(0);
- + uc_value_t *newfd_arg = uc_fn_arg(1);
- + int oldfd, newfd;
- +
- + oldfd = get_fd(vm, oldfd_arg);
- +
- + if (oldfd == -1)
- + err_return(errno ? errno : EBADF);
- +
- + newfd = get_fd(vm, newfd_arg);
- +
- + if (newfd == -1)
- + err_return(errno ? errno : EBADF);
- +
- + if (dup2(oldfd, newfd) == -1)
- + err_return(errno);
- +
- + return ucv_boolean_new(true);
- +}
- +
-
- /**
- * Represents a handle for interacting with a directory opened by `opendir()`.
- @@ -2890,6 +2938,7 @@ static const uc_function_list_t global_f
- { "error", uc_fs_error },
- { "open", uc_fs_open },
- { "fdopen", uc_fs_fdopen },
- + { "dup2", uc_fs_dup2 },
- { "opendir", uc_fs_opendir },
- { "popen", uc_fs_popen },
- { "readlink", uc_fs_readlink },
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