HADOOP-9483. Adding a file missed in previous commit r1478592
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1478633 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Suresh Srinivas
parent
fc275fed66
commit
4b93035997
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/**
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with this
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* work for additional information regarding copyright ownership. The ASF
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* licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*/
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#include "winutils.h"
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//----------------------------------------------------------------------------
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// The Windows SDK does not include the definition of REPARSE_DATA_BUFFER. To
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// avoid adding a dependency on the WDK we define the structure here.
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// Reference: http://msdn.microsoft.com/en-us/library/ff552012.aspx
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//
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#pragma warning(push)
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#pragma warning(disable: 4201) // nonstandard extension: nameless struct/union
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#pragma pack(push, 1)
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typedef struct _REPARSE_DATA_BUFFER {
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ULONG ReparseTag;
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USHORT ReparseDataLength;
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USHORT Reserved;
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union {
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struct {
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USHORT SubstituteNameOffset;
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USHORT SubstituteNameLength;
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USHORT PrintNameOffset;
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USHORT PrintNameLength;
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ULONG Flags;
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WCHAR PathBuffer[1];
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} SymbolicLinkReparseBuffer;
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struct {
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USHORT SubstituteNameOffset;
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USHORT SubstituteNameLength;
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USHORT PrintNameOffset;
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USHORT PrintNameLength;
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WCHAR PathBuffer[1];
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} MountPointReparseBuffer;
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struct {
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UCHAR DataBuffer[1];
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} GenericReparseBuffer;
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};
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} REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;
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#pragma pack(pop)
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#pragma warning(pop)
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//----------------------------------------------------------------------------
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// Function: Readlink
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//
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// Description:
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// Prints the target of a symbolic link to stdout.
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//
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// The return codes and output are modeled after the UNIX readlink command.
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// Hence no error messages are printed. Unlike the UNIX readlink, no options
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// are accepted.
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//
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// Returns:
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// 0: on success
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// 1: on all errors
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//
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// Notes:
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//
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int Readlink(__in int argc, __in_ecount(argc) wchar_t *argv[])
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{
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DWORD bytesReturned;
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DWORD bufferSize = 1024; // Start off with a 1KB buffer.
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HANDLE hFile = INVALID_HANDLE_VALUE;
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PWSTR longLinkName = NULL;
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PWCHAR printName = NULL;
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PREPARSE_DATA_BUFFER pReparseData = NULL;
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USHORT printNameLength;
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USHORT printNameOffset;
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DWORD result;
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BOOLEAN succeeded = FALSE;
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if (argc != 2)
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{
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ReadlinkUsage();
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goto Cleanup;
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}
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if (ConvertToLongPath(argv[1], &longLinkName) != ERROR_SUCCESS)
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{
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goto Cleanup;
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}
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// Get a handle to the link to issue the FSCTL.
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// FILE_FLAG_BACKUP_SEMANTICS is needed to open directories.
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// FILE_FLAG_OPEN_REPARSE_POINT disables normal reparse point processing
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// so we can query the symlink.
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//
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hFile = CreateFileW(longLinkName,
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0, // no rights needed to issue the FSCTL.
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FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
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NULL,
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OPEN_EXISTING,
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FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
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NULL);
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if (hFile == INVALID_HANDLE_VALUE)
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{
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goto Cleanup;
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}
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for (;;)
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{
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pReparseData = (PREPARSE_DATA_BUFFER) LocalAlloc(LMEM_FIXED, bufferSize);
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if (pReparseData == NULL)
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{
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goto Cleanup;
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}
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// Issue the FSCTL to query the link information.
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//
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result = DeviceIoControl(hFile,
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FSCTL_GET_REPARSE_POINT,
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NULL,
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0,
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pReparseData,
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bufferSize,
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&bytesReturned,
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NULL);
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if (result != 0)
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{
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// Success!
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//
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break;
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}
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else if ((GetLastError() == ERROR_INSUFFICIENT_BUFFER) ||
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(GetLastError() == ERROR_MORE_DATA))
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{
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// Retry with a larger buffer.
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//
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LocalFree(pReparseData);
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bufferSize *= 2;
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}
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else
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{
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// Unrecoverable error.
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//
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goto Cleanup;
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}
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}
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if (pReparseData->ReparseTag != IO_REPARSE_TAG_SYMLINK)
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{
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// Doesn't look like a symlink.
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//
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goto Cleanup;
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}
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// MSDN does not guarantee that the embedded paths in REPARSE_DATA_BUFFER
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// will be NULL terminated. So we copy the string to a separate buffer and
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// NULL terminate it before printing.
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//
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printNameLength = pReparseData->SymbolicLinkReparseBuffer.PrintNameLength;
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printNameOffset = pReparseData->SymbolicLinkReparseBuffer.PrintNameOffset;
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printName = (PWCHAR) LocalAlloc(LMEM_FIXED, printNameLength + 1);
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if (printName == NULL)
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{
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goto Cleanup;
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}
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memcpy(
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printName,
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pReparseData->SymbolicLinkReparseBuffer.PathBuffer + printNameOffset,
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printNameLength);
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printName[printNameLength / sizeof(WCHAR)] = L'\0';
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fwprintf(stdout, L"%ls", printName);
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succeeded = TRUE;
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Cleanup:
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if (hFile != INVALID_HANDLE_VALUE)
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{
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CloseHandle(hFile);
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}
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if (printName != NULL)
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{
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LocalFree(printName);
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}
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if (pReparseData != NULL)
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{
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LocalFree(pReparseData);
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}
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if (longLinkName != NULL)
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{
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LocalFree(longLinkName);
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}
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return (succeeded ? EXIT_SUCCESS : EXIT_FAILURE);
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}
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void ReadlinkUsage()
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{
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fwprintf(stdout, L"\
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Usage: readlink [LINKNAME]\n\
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Prints the target of a symbolic link\n\
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The output and returned error codes are similar to the UNIX\n\
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readlink command. However no options are accepted.\n\
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\n\
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0 is returned on success.\n\
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1 is returned for all errors.\n\
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\n");
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}
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