file

File manipulation command.

This command is dedicated to file and path manipulation requiring access to the filesystem.

For other path manipulation, handling only syntactic aspects, have a look at cmake_path() command.

Note

The sub-commands RELATIVE_PATH, TO_CMAKE_PATH and TO_NATIVE_PATH has been superseded, respectively, by sub-commands RELATIVE_PATH, CONVERT ... TO_CMAKE_PATH_LIST and CONVERT ... TO_NATIVE_PATH_LIST of cmake_path() command.

Synopsis

Reading
  file(READ <filename> <out-var> [...])
  file(STRINGS <filename> <out-var> [...])
  file(<HASH> <filename> <out-var>)
  file(TIMESTAMP <filename> <out-var> [...])
  file(GET_RUNTIME_DEPENDENCIES [...])

Writing
  file({WRITE | APPEND} <filename> <content>...)
  file({TOUCH | TOUCH_NOCREATE} <file>...)
  file(GENERATE OUTPUT <output-file> [...])
  file(CONFIGURE OUTPUT <output-file> CONTENT <content> [...])

Filesystem
  file({GLOB | GLOB_RECURSE} <out-var> [...] <globbing-expr>...)
  file(MAKE_DIRECTORY <directories>...)
  file({REMOVE | REMOVE_RECURSE } <files>...)
  file(RENAME <oldname> <newname> [...])
  file(COPY_FILE <oldname> <newname> [...])
  file({COPY | INSTALL} <file>... DESTINATION <dir> [...])
  file(SIZE <filename> <out-var>)
  file(READ_SYMLINK <linkname> <out-var>)
  file(CREATE_LINK <original> <linkname> [...])
  file(CHMOD <files>... <directories>... PERMISSIONS <permissions>... [...])
  file(CHMOD_RECURSE <files>... <directories>... PERMISSIONS <permissions>... [...])

Path Conversion
  file(REAL_PATH <path> <out-var> [BASE_DIRECTORY <dir>] [EXPAND_TILDE])
  file(RELATIVE_PATH <out-var> <directory> <file>)
  file({TO_CMAKE_PATH | TO_NATIVE_PATH} <path> <out-var>)

Transfer
  file(DOWNLOAD <url> [<file>] [...])
  file(UPLOAD <file> <url> [...])

Locking
  file(LOCK <path> [...])

Archiving
  file(ARCHIVE_CREATE OUTPUT <archive> PATHS <paths>... [...])
  file(ARCHIVE_EXTRACT INPUT <archive> [...])

Reading

file(READ <filename> <variable> [OFFSET <offset>] [LIMIT <max-in>] [HEX])

Read content from a file called <filename> and store it in a <variable>. Optionally start from the given <offset> and read at most <max-in> bytes. The HEX option causes data to be converted to a hexadecimal representation (useful for binary data). If the HEX option is specified, letters in the output (a through f) are in lowercase.

file(STRINGS <filename> <variable> <options>...)

Parse a list of ASCII strings from <filename> and store it in <variable>. Binary data in the file are ignored. Carriage return (\r, CR) characters are ignored. The options are:

LENGTH_MAXIMUM <max-len>

Consider only strings of at most a given length.

LENGTH_MINIMUM <min-len>

Consider only strings of at least a given length.

LIMIT_COUNT <max-num>

Limit the number of distinct strings to be extracted.

LIMIT_INPUT <max-in>

Limit the number of input bytes to read from the file.

LIMIT_OUTPUT <max-out>

Limit the number of total bytes to store in the <variable>.

NEWLINE_CONSUME

Treat newline characters (\n, LF) as part of string content instead of terminating at them.

NO_HEX_CONVERSION

Intel Hex and Motorola S-record files are automatically converted to binary while reading unless this option is given.

REGEX <regex>

Consider only strings that match the given regular expression, as described under string(REGEX).

Changed in version 3.29: Capture groups from the last match in the file are stored in CMAKE_MATCH_<n>, similar to string(REGEX MATCHALL). See policy CMP0159.

ENCODING <encoding-type>

New in version 3.1.

Consider strings of a given encoding. Currently supported encodings are: UTF-8, UTF-16LE, UTF-16BE, UTF-32LE, UTF-32BE. If the ENCODING option is not provided and the file has a Byte Order Mark, the ENCODING option will be defaulted to respect the Byte Order Mark.

New in version 3.2: Added the UTF-16LE, UTF-16BE, UTF-32LE, UTF-32BE encodings.

For example, the code

file(STRINGS myfile.txt myfile)

stores a list in the variable myfile in which each item is a line from the input file.

file(<HASH> <filename> <variable>)

Compute a cryptographic hash of the content of <filename> and store it in a <variable>. The supported <HASH> algorithm names are those listed by the string(<HASH>) command.

file(TIMESTAMP <filename> <variable> [<format>] [UTC])

Compute a string representation of the modification time of <filename> and store it in <variable>. Should the command be unable to obtain a timestamp variable will be set to the empty string ("").

See the string(TIMESTAMP) command for documentation of the <format> and UTC options.

file(GET_RUNTIME_DEPENDENCIES [...])

New in version 3.16.

Recursively get the list of libraries depended on by the given files:

file(GET_RUNTIME_DEPENDENCIES
  [RESOLVED_DEPENDENCIES_VAR <deps_var>]
  [UNRESOLVED_DEPENDENCIES_VAR <unresolved_deps_var>]
  [CONFLICTING_DEPENDENCIES_PREFIX <conflicting_deps_prefix>]
  [EXECUTABLES <executable_files>...]
  [LIBRARIES <library_files>...]
  [MODULES <module_files>...]
  [DIRECTORIES <directories>...]
  [BUNDLE_EXECUTABLE <bundle_executable_file>]
  [PRE_INCLUDE_REGEXES <regexes>...]
  [PRE_EXCLUDE_REGEXES <regexes>...]
  [POST_INCLUDE_REGEXES <regexes>...]
  [POST_EXCLUDE_REGEXES <regexes>...]
  [POST_INCLUDE_FILES <files>...]
  [POST_EXCLUDE_FILES <files>...]
  )

Please note that this sub-command is not intended to be used in project mode. It is intended for use at install time, either from code generated by the install(RUNTIME_DEPENDENCY_SET) command, or from code provided by the project via install(CODE) or install(SCRIPT). For example:

install(CODE [[
  file(GET_RUNTIME_DEPENDENCIES
    # ...
    )
  ]])

The arguments are as follows:

RESOLVED_DEPENDENCIES_VAR <deps_var>

Name of the variable in which to store the list of resolved dependencies.

UNRESOLVED_DEPENDENCIES_VAR <unresolved_deps_var>

Name of the variable in which to store the list of unresolved dependencies. If this variable is not specified, and there are any unresolved dependencies, an error is issued.

CONFLICTING_DEPENDENCIES_PREFIX <conflicting_deps_prefix>

Variable prefix in which to store conflicting dependency information. Dependencies are conflicting if two files with the same name are found in two different directories. The list of filenames that conflict are stored in <conflicting_deps_prefix>_FILENAMES. For each filename, the list of paths that were found for that filename are stored in <conflicting_deps_prefix>_<filename>.

EXECUTABLES <executable_files>...

List of executable files to read for dependencies. These are executables that are typically created with add_executable(), but they do not have to be created by CMake. On Apple platforms, the paths to these files determine the value of @executable_path when recursively resolving the libraries. Specifying any kind of library (STATIC, MODULE, or SHARED) here will result in undefined behavior.

LIBRARIES <library_files>...

List of library files to read for dependencies. These are libraries that are typically created with add_library(SHARED), but they do not have to be created by CMake. Specifying STATIC libraries, MODULE libraries, or executables here will result in undefined behavior.

MODULES <module_files>...

List of loadable module files to read for dependencies. These are modules that are typically created with add_library(MODULE), but they do not have to be created by CMake. They are typically used by calling dlopen() at runtime rather than linked at link time with ld -l. Specifying STATIC libraries, SHARED libraries, or executables here will result in undefined behavior.

DIRECTORIES <directories>...

List of additional directories to search for dependencies. On Linux platforms, these directories are searched if the dependency is not found in any of the other usual paths. If it is found in such a directory, a warning is issued, because it means that the file is incomplete (it does not list all of the directories that contain its dependencies). On Windows platforms, these directories are searched if the dependency is not found in any of the other search paths, but no warning is issued, because searching other paths is a normal part of Windows dependency resolution. On Apple platforms, this argument has no effect.

BUNDLE_EXECUTABLE <bundle_executable_file>

Executable to treat as the "bundle executable" when resolving libraries. On Apple platforms, this argument determines the value of @executable_path when recursively resolving libraries for LIBRARIES and MODULES files. It has no effect on EXECUTABLES files. On other platforms, it has no effect. This is typically (but not always) one of the executables in the EXECUTABLES argument which designates the "main" executable of the package.

The following arguments specify filters for including or excluding libraries to be resolved. See below for a full description of how they work.

PRE_INCLUDE_REGEXES <regexes>...

List of pre-include regexes through which to filter the names of not-yet-resolved dependencies.

PRE_EXCLUDE_REGEXES <regexes>...

List of pre-exclude regexes through which to filter the names of not-yet-resolved dependencies.

POST_INCLUDE_REGEXES <regexes>...

List of post-include regexes through which to filter the names of resolved dependencies.

POST_EXCLUDE_REGEXES <regexes>...

List of post-exclude regexes through which to filter the names of resolved dependencies.

POST_INCLUDE_FILES <files>...

New in version 3.21.

List of post-include filenames through which to filter the names of resolved dependencies. Symlinks are resolved when attempting to match these filenames.

POST_EXCLUDE_FILES <files>...

New in version 3.21.

List of post-exclude filenames through which to filter the names of resolved dependencies. Symlinks are resolved when attempting to match these filenames.

These arguments can be used to exclude unwanted system libraries when resolving the dependencies, or to include libraries from a specific directory. The filtering works as follows:

1. If the not-yet-resolved dependency matches any of the PRE_INCLUDE_REGEXES, steps 2 and 3 are skipped, and the dependency resolution proceeds to step 4.

2. If the not-yet-resolved dependency matches any of the PRE_EXCLUDE_REGEXES, dependency resolution stops for that dependency.

3. Otherwise, dependency resolution proceeds.

4. file(GET_RUNTIME_DEPENDENCIES) searches for the dependency according to the linking rules of the platform (see below).

5. If the dependency is found, and its full path matches one of the POST_INCLUDE_REGEXES or POST_INCLUDE_FILES, the full path is added to the resolved dependencies, and file(GET_RUNTIME_DEPENDENCIES) recursively resolves that library's own dependencies. Otherwise, resolution proceeds to step 6.

6. If the dependency is found, but its full path matches one of the POST_EXCLUDE_REGEXES or POST_EXCLUDE_FILES, it is not added to the resolved dependencies, and dependency resolution stops for that dependency.

7. If the dependency is found, and its full path does not match either POST_INCLUDE_REGEXES, POST_INCLUDE_FILES, POST_EXCLUDE_REGEXES, or POST_EXCLUDE_FILES, the full path is added to the resolved dependencies, and file(GET_RUNTIME_DEPENDENCIES) recursively resolves that library's own dependencies.

Different platforms have different rules for how dependencies are resolved. These specifics are described here.

On Linux platforms, library resolution works as follows:

1. If the depending file does not have any RUNPATH entries, and the library exists in one of the depending file's RPATH entries, or its parents', in that order, the dependency is resolved to that file.

2. Otherwise, if the depending file has any RUNPATH entries, and the library exists in one of those entries, the dependency is resolved to that file.

3. Otherwise, if the library exists in one of the directories listed by ldconfig, the dependency is resolved to that file.

4. Otherwise, if the library exists in one of the DIRECTORIES entries, the dependency is resolved to that file. In this case, a warning is issued, because finding a file in one of the DIRECTORIES means that the depending file is not complete (it does not list all the directories from which it pulls dependencies).

5. Otherwise, the dependency is unresolved.

On Windows platforms, library resolution works as follows:

1. DLL dependency names are converted to lowercase for matching filters. Windows DLL names are case-insensitive, and some linkers mangle the case of the DLL dependency names. However, this makes it more difficult for PRE_INCLUDE_REGEXES, PRE_EXCLUDE_REGEXES, POST_INCLUDE_REGEXES, and POST_EXCLUDE_REGEXES to properly filter DLL names - every regex would have to check for both uppercase and lowercase letters. For example:

   file(GET_RUNTIME_DEPENDENCIES
     # ...
     PRE_INCLUDE_REGEXES "^[Mm][Yy][Ll][Ii][Bb][Rr][Aa][Rr][Yy]\\.[Dd][Ll][Ll]$"
     )
   

   Converting the DLL name to lowercase allows the regexes to only match lowercase names, thus simplifying the regex. For example:

   file(GET_RUNTIME_DEPENDENCIES
     # ...
     PRE_INCLUDE_REGEXES "^mylibrary\\.dll$"
     )
   

   This regex will match mylibrary.dll regardless of how it is cased, either on disk or in the depending file. (For example, it will match mylibrary.dll, MyLibrary.dll, and MYLIBRARY.DLL.)

   Changed in version 3.27: The conversion to lowercase only applies while matching filters. Results reported after filtering case-preserve each DLL name as it is found on disk, if resolved, and otherwise as it is referenced by the dependent binary.

   Prior to CMake 3.27, the results were reported with lowercase DLL file names, but the directory portion retained its casing.

2. (Not yet implemented) If the depending file is a Windows Store app, and the dependency is listed as a dependency in the application's package manifest, the dependency is resolved to that file.

3. Otherwise, if the library exists in the same directory as the depending file, the dependency is resolved to that file.

4. Otherwise, if the library exists in either the operating system's system32 directory or the Windows directory, in that order, the dependency is resolved to that file.

5. Otherwise, if the library exists in one of the directories specified by DIRECTORIES, in the order they are listed, the dependency is resolved to that file. In this case, a warning is not issued, because searching other directories is a normal part of Windows library resolution.

6. Otherwise, the dependency is unresolved.

On Apple platforms, library resolution works as follows:

1. If the dependency starts with @executable_path/, and an EXECUTABLES argument is in the process of being resolved, and replacing @executable_path/ with the directory of the executable yields an existing file, the dependency is resolved to that file.

2. Otherwise, if the dependency starts with @executable_path/, and there is a BUNDLE_EXECUTABLE argument, and replacing @executable_path/ with the directory of the bundle executable yields an existing file, the dependency is resolved to that file.

3. Otherwise, if the dependency starts with @loader_path/, and replacing @loader_path/ with the directory of the depending file yields an existing file, the dependency is resolved to that file.

4. Otherwise, if the dependency starts with @rpath/, and replacing @rpath/ with one of the RPATH entries of the depending file yields an existing file, the dependency is resolved to that file. Note that RPATH entries that start with @executable_path/ or @loader_path/ also have these items replaced with the appropriate path.

5. Otherwise, if the dependency is an absolute file that exists, the dependency is resolved to that file.

6. Otherwise, the dependency is unresolved.

This function accepts several variables that determine which tool is used for dependency resolution:

CMAKE_GET_RUNTIME_DEPENDENCIES_PLATFORM

Determines which operating system and executable format the files are built for. This could be one of several values:

• linux+elf

• windows+pe

• macos+macho

If this variable is not specified, it is determined automatically by system introspection.

CMAKE_GET_RUNTIME_DEPENDENCIES_TOOL

Determines the tool to use for dependency resolution. It could be one of several values, depending on the value of CMAKE_GET_RUNTIME_DEPENDENCIES_PLATFORM:

CMAKE_GET_RUNTIME_DEPENDENCIES_PLATFORM	CMAKE_GET_RUNTIME_DEPENDENCIES_TOOL
linux+elf	objdump
windows+pe	objdump or dumpbin
macos+macho	otool

If this variable is not specified, it is determined automatically by system introspection.

CMAKE_GET_RUNTIME_DEPENDENCIES_COMMAND

Determines the path to the tool to use for dependency resolution. This is the actual path to objdump, dumpbin, or otool.

If this variable is not specified, it is determined by the value of CMAKE_OBJDUMP if set, else by system introspection.

New in version 3.18: Use CMAKE_OBJDUMP if set.

Writing

file(WRITE <filename> <content>...)

file(APPEND <filename> <content>...)

Write <content> into a file called <filename>. If the file does not exist, it will be created. If the file already exists, WRITE mode will overwrite it and APPEND mode will append to the end. Any directories in the path specified by <filename> that do not exist will be created.

If the file is a build input, use the configure_file() command to update the file only when its content changes.

file(TOUCH <files>...)

file(TOUCH_NOCREATE <files>...)

New in version 3.12.

Create a file with no content if it does not yet exist. If the file already exists, its access and/or modification will be updated to the time when the function call is executed.

Use TOUCH_NOCREATE to touch a file if it exists but not create it. If a file does not exist it will be silently ignored.

With TOUCH and TOUCH_NOCREATE, the contents of an existing file will not be modified.

file(GENERATE [...])

Generate an output file for each build configuration supported by the current CMake Generator. Evaluate generator expressions from the input content to produce the output content.

file(GENERATE OUTPUT <output-file>
     <INPUT <input-file>|CONTENT <content>>
     [CONDITION <expression>] [TARGET <target>]
     [NO_SOURCE_PERMISSIONS | USE_SOURCE_PERMISSIONS |
      FILE_PERMISSIONS <permissions>...]
     [NEWLINE_STYLE [UNIX|DOS|WIN32|LF|CRLF] ])

The options are:

CONDITION <condition>

Generate the output file for a particular configuration only if the condition is true. The condition must be either 0 or 1 after evaluating generator expressions.

CONTENT <content>

Use the content given explicitly as input.

INPUT <input-file>

Use the content from a given file as input.

Changed in version 3.10: A relative path is treated with respect to the value of CMAKE_CURRENT_SOURCE_DIR. See policy CMP0070.

OUTPUT <output-file>

Specify the output file name to generate. Use generator expressions such as $<CONFIG> to specify a configuration-specific output file name. Multiple configurations may generate the same output file only if the generated content is identical. Otherwise, the <output-file> must evaluate to an unique name for each configuration.

Changed in version 3.10: A relative path (after evaluating generator expressions) is treated with respect to the value of CMAKE_CURRENT_BINARY_DIR. See policy CMP0070.

TARGET <target>

New in version 3.19.

Specify which target to use when evaluating generator expressions that require a target for evaluation (e.g. $<COMPILE_FEATURES:...>, $<TARGET_PROPERTY:prop>).

NO_SOURCE_PERMISSIONS

New in version 3.20.

The generated file permissions default to the standard 644 value (-rw-r--r--).

USE_SOURCE_PERMISSIONS

New in version 3.20.

Transfer the file permissions of the INPUT file to the generated file. This is already the default behavior if none of the three permissions-related keywords are given (NO_SOURCE_PERMISSIONS, USE_SOURCE_PERMISSIONS or FILE_PERMISSIONS). The USE_SOURCE_PERMISSIONS keyword mostly serves as a way of making the intended behavior clearer at the call site. It is an error to specify this option without INPUT.

FILE_PERMISSIONS <permissions>...

New in version 3.20.

Use the specified permissions for the generated file.

NEWLINE_STYLE <style>

New in version 3.20.

Specify the newline style for the generated file. Specify UNIX or LF for \n newlines, or specify DOS, WIN32, or CRLF for \r\n newlines.

Exactly one CONTENT or INPUT option must be given. A specific OUTPUT file may be named by at most one invocation of file(GENERATE). Generated files are modified and their timestamp updated on subsequent cmake runs only if their content is changed.

Note also that file(GENERATE) does not create the output file until the generation phase. The output file will not yet have been written when the file(GENERATE) command returns, it is written only after processing all of a project's CMakeLists.txt files.

file(CONFIGURE OUTPUT <output-file> CONTENT <content> [ESCAPE_QUOTES] [@ONLY] [NEWLINE_STYLE [UNIX|DOS|WIN32|LF|CRLF] ])

New in version 3.18.

Generate an output file using the input given by CONTENT and substitute variable values referenced as @VAR@ or ${VAR} contained therein. The substitution rules behave the same as the configure_file() command. In order to match configure_file()'s behavior, generator expressions are not supported for both OUTPUT and CONTENT.

The arguments are:

OUTPUT <output-file>

Specify the output file name to generate. A relative path is treated with respect to the value of CMAKE_CURRENT_BINARY_DIR. <output-file> does not support generator expressions.

CONTENT <content>

Use the content given explicitly as input. <content> does not support generator expressions.

ESCAPE_QUOTES

Escape any substituted quotes with backslashes (C-style).

@ONLY

Restrict variable replacement to references of the form @VAR@. This is useful for configuring scripts that use ${VAR} syntax.

NEWLINE_STYLE <style>

Specify the newline style for the output file. Specify UNIX or LF for \n newlines, or specify DOS, WIN32, or CRLF for \r\n newlines.

Filesystem

file(GLOB <variable> [LIST_DIRECTORIES true|false] [RELATIVE <path>] [CONFIGURE_DEPENDS] <globbing-expressions>...)

file(GLOB_RECURSE <variable> [FOLLOW_SYMLINKS] [LIST_DIRECTORIES true|false] [RELATIVE <path>] [CONFIGURE_DEPENDS] <globbing-expressions>...)

Generate a list of files that match the <globbing-expressions> and store it into the <variable>. Globbing expressions are similar to regular expressions, but much simpler. If RELATIVE flag is specified, the results will be returned as relative paths to the given path.

Changed in version 3.6: The results will be ordered lexicographically.

On Windows and macOS, globbing is case-insensitive even if the underlying filesystem is case-sensitive (both filenames and globbing expressions are converted to lowercase before matching). On other platforms, globbing is case-sensitive.

New in version 3.3: By default GLOB lists directories. Directories are omitted in the result if LIST_DIRECTORIES is set to false.

New in version 3.12: If the CONFIGURE_DEPENDS flag is specified, CMake will add logic to the main build system check target to rerun the flagged GLOB commands at build time. If any of the outputs change, CMake will regenerate the build system.

Note

We do not recommend using GLOB to collect a list of source files from your source tree. If no CMakeLists.txt file changes when a source is added or removed then the generated build system cannot know when to ask CMake to regenerate. The CONFIGURE_DEPENDS flag may not work reliably on all generators, or if a new generator is added in the future that cannot support it, projects using it will be stuck. Even if CONFIGURE_DEPENDS works reliably, there is still a cost to perform the check on every rebuild.

Examples of globbing expressions include:

*.cxx	match all files with extension cxx
*.vt?	match all files with extension vta, ..., vtz
f[3-5].txt	match files f3.txt, f4.txt, f5.txt

The GLOB_RECURSE mode will traverse all the subdirectories of the matched directory and match the files. Subdirectories that are symlinks are only traversed if FOLLOW_SYMLINKS is given or policy CMP0009 is not set to NEW.

New in version 3.3: By default GLOB_RECURSE omits directories from result list. Setting LIST_DIRECTORIES to true adds directories to result list. If FOLLOW_SYMLINKS is given or policy CMP0009 is not set to NEW then LIST_DIRECTORIES treats symlinks as directories.

Examples of recursive globbing include:

/dir/*.py

match all python files in /dir and subdirectories

file(MAKE_DIRECTORY <directories>...)

Create the given directories and their parents as needed.

file(REMOVE <files>...)

file(REMOVE_RECURSE <files>...)

Remove the given files. The REMOVE_RECURSE mode will remove the given files and directories, including non-empty directories. No error is emitted if a given file does not exist. Relative input paths are evaluated with respect to the current source directory.

Changed in version 3.15: Empty input paths are ignored with a warning. Previous versions of CMake interpreted empty strings as a relative path with respect to the current directory and removed its contents.

file(RENAME <oldname> <newname> [RESULT <result>] [NO_REPLACE])

Move a file or directory within a filesystem from <oldname> to <newname>, replacing the destination atomically.

The options are:

RESULT <result>

New in version 3.21.

Set <result> variable to 0 on success or an error message otherwise. If RESULT is not specified and the operation fails, an error is emitted.

NO_REPLACE

New in version 3.21.

If the <newname> path already exists, do not replace it. If RESULT <result> is used, the result variable will be set to NO_REPLACE. Otherwise, an error is emitted.

file(COPY_FILE <oldname> <newname> [RESULT <result>] [ONLY_IF_DIFFERENT] [INPUT_MAY_BE_RECENT])

New in version 3.21.

Copy a file from <oldname> to <newname>. Directories are not supported. Symlinks are ignored and <oldfile>'s content is read and written to <newname> as a new file.

The options are:

RESULT <result>

Set <result> variable to 0 on success or an error message otherwise. If RESULT is not specified and the operation fails, an error is emitted.

ONLY_IF_DIFFERENT

If the <newname> path already exists, do not replace it if the file's contents are already the same as <oldname> (this avoids updating <newname>'s timestamp).

INPUT_MAY_BE_RECENT

New in version 3.26.

Tell CMake that the input file may have been recently created. This is meaningful only on Windows, where files may be inaccessible for a short time after they are created. With this option, if permission is denied, CMake will retry reading the input a few times.

This sub-command has some similarities to configure_file() with the COPYONLY option. An important difference is that configure_file() creates a dependency on the source file, so CMake will be re-run if it changes. The file(COPY_FILE) sub-command does not create such a dependency.

See also the file(COPY) sub-command just below which provides further file-copying capabilities.

file(COPY [...])

file(INSTALL [...])

The COPY signature copies files, directories, and symlinks to a destination folder. Relative input paths are evaluated with respect to the current source directory, and a relative destination is evaluated with respect to the current build directory. Copying preserves input file timestamps, and optimizes out a file if it exists at the destination with the same timestamp. Copying preserves input permissions unless explicit permissions or NO_SOURCE_PERMISSIONS are given (default is USE_SOURCE_PERMISSIONS).

file(<COPY|INSTALL> <files>... DESTINATION <dir>
     [NO_SOURCE_PERMISSIONS | USE_SOURCE_PERMISSIONS]
     [FILE_PERMISSIONS <permissions>...]
     [DIRECTORY_PERMISSIONS <permissions>...]
     [FOLLOW_SYMLINK_CHAIN]
     [FILES_MATCHING]
     [[PATTERN <pattern> | REGEX <regex>]
      [EXCLUDE] [PERMISSIONS <permissions>...]] [...])

Note

For a simple file copying operation, the file(COPY_FILE) sub-command just above may be easier to use.

New in version 3.15: If FOLLOW_SYMLINK_CHAIN is specified, COPY will recursively resolve the symlinks at the paths given until a real file is found, and install a corresponding symlink in the destination for each symlink encountered. For each symlink that is installed, the resolution is stripped of the directory, leaving only the filename, meaning that the new symlink points to a file in the same directory as the symlink. This feature is useful on some Unix systems, where libraries are installed as a chain of symlinks with version numbers, with less specific versions pointing to more specific versions. FOLLOW_SYMLINK_CHAIN will install all of these symlinks and the library itself into the destination directory. For example, if you have the following directory structure:

• /opt/foo/lib/libfoo.so.1.2.3

• /opt/foo/lib/libfoo.so.1.2 -> libfoo.so.1.2.3

• /opt/foo/lib/libfoo.so.1 -> libfoo.so.1.2

• /opt/foo/lib/libfoo.so -> libfoo.so.1

and you do:

file(COPY /opt/foo/lib/libfoo.so DESTINATION lib FOLLOW_SYMLINK_CHAIN)

This will install all of the symlinks and libfoo.so.1.2.3 itself into lib.

See the install(DIRECTORY) command for documentation of permissions, FILES_MATCHING, PATTERN, REGEX, and EXCLUDE options. Copying directories preserves the structure of their content even if options are used to select a subset of files.

The INSTALL signature differs slightly from COPY: it prints status messages, and NO_SOURCE_PERMISSIONS is default. Installation scripts generated by the install() command use this signature (with some undocumented options for internal use).

Changed in version 3.22: The environment variable CMAKE_INSTALL_MODE can override the default copying behavior of file(INSTALL).

file(SIZE <filename> <variable>)

New in version 3.14.

Determine the file size of the <filename> and put the result in <variable> variable. Requires that <filename> is a valid path pointing to a file and is readable.

file(READ_SYMLINK <linkname> <variable>)

New in version 3.14.

Query the symlink <linkname> and stores the path it points to in the result <variable>. If <linkname> does not exist or is not a symlink, CMake issues a fatal error.

Note that this command returns the raw symlink path and does not resolve a relative path. The following is an example of how to ensure that an absolute path is obtained:

set(linkname "/path/to/foo.sym")
file(READ_SYMLINK "${linkname}" result)
if(NOT IS_ABSOLUTE "${result}")
  get_filename_component(dir "${linkname}" DIRECTORY)
  set(result "${dir}/${result}")
endif()

file(CREATE_LINK <original> <linkname> [RESULT <result>] [COPY_ON_ERROR] [SYMBOLIC])

New in version 3.14.

Create a link <linkname> that points to <original>. It will be a hard link by default, but providing the SYMBOLIC option results in a symbolic link instead. Hard links require that original exists and is a file, not a directory. If <linkname> already exists, it will be overwritten.

The <result> variable, if specified, receives the status of the operation. It is set to 0 upon success or an error message otherwise. If RESULT is not specified and the operation fails, a fatal error is emitted.

Specifying COPY_ON_ERROR enables copying the file as a fallback if creating the link fails. It can be useful for handling situations such as <original> and <linkname> being on different drives or mount points, which would make them unable to support a hard link.

file(CHMOD <files>... <directories>... [PERMISSIONS <permissions>...] [FILE_PERMISSIONS <permissions>...] [DIRECTORY_PERMISSIONS <permissions>...])

New in version 3.19.

Set the permissions for the <files>... and <directories>... specified. Valid permissions are OWNER_READ, OWNER_WRITE, OWNER_EXECUTE, GROUP_READ, GROUP_WRITE, GROUP_EXECUTE, WORLD_READ, WORLD_WRITE, WORLD_EXECUTE, SETUID, SETGID.

Valid combination of keywords are:

PERMISSIONS

All items are changed.

FILE_PERMISSIONS

Only files are changed.

DIRECTORY_PERMISSIONS

Only directories are changed.

PERMISSIONS and FILE_PERMISSIONS

FILE_PERMISSIONS overrides PERMISSIONS for files.

PERMISSIONS and DIRECTORY_PERMISSIONS

DIRECTORY_PERMISSIONS overrides PERMISSIONS for directories.

FILE_PERMISSIONS and DIRECTORY_PERMISSIONS

Use FILE_PERMISSIONS for files and DIRECTORY_PERMISSIONS for directories.

file(CHMOD_RECURSE <files>... <directories>... [PERMISSIONS <permissions>...] [FILE_PERMISSIONS <permissions>...] [DIRECTORY_PERMISSIONS <permissions>...])

New in version 3.19.

Same as CHMOD, but change the permissions of files and directories present in the <directories>... recursively.

Path Conversion

file(REAL_PATH <path> <out-var> [BASE_DIRECTORY <dir>] [EXPAND_TILDE])

New in version 3.19.

Compute the absolute path to an existing file or directory with symlinks resolved. The options are:

BASE_DIRECTORY <dir>

If the provided <path> is a relative path, it is evaluated relative to the given base directory <dir>. If no base directory is provided, the default base directory will be CMAKE_CURRENT_SOURCE_DIR.

EXPAND_TILDE

New in version 3.21.

If the <path> is ~ or starts with ~/, the ~ is replaced by the user's home directory. The path to the home directory is obtained from environment variables. On Windows, the USERPROFILE environment variable is used, falling back to the HOME environment variable if USERPROFILE is not defined. On all other platforms, only HOME is used.

Changed in version 3.28: All symlinks are resolved before collapsing ../ components. See policy CMP0152.

file(RELATIVE_PATH <variable> <directory> <file>)

Compute the relative path from a <directory> to a <file> and store it in the <variable>.

file(TO_CMAKE_PATH "<path>" <variable>)

file(TO_NATIVE_PATH "<path>" <variable>)

The TO_CMAKE_PATH mode converts a native <path> into a cmake-style path with forward-slashes (/). The input can be a single path or a system search path like $ENV{PATH}. A search path will be converted to a cmake-style list separated by ; characters.

The TO_NATIVE_PATH mode converts a cmake-style <path> into a native path with platform-specific slashes (\ on Windows hosts and / elsewhere).

Always use double quotes around the <path> to be sure it is treated as a single argument to this command.

Transfer

file(DOWNLOAD <url> [<file>] <options>...)

file(UPLOAD <file> <url> <options>...)

The DOWNLOAD subcommand downloads the given <url> to a local <file>. The UPLOAD mode uploads a local <file> to a given <url>.

New in version 3.19: If <file> is not specified for file(DOWNLOAD), the file is not saved. This can be useful if you want to know if a file can be downloaded (for example, to check that it exists) without actually saving it anywhere.

Options to both DOWNLOAD and UPLOAD are:

INACTIVITY_TIMEOUT <seconds>

Terminate the operation after a period of inactivity.

LOG <variable>

Store a human-readable log of the operation in a variable.

SHOW_PROGRESS

Print progress information as status messages until the operation is complete.

STATUS <variable>

Store the resulting status of the operation in a variable. The status is a ; separated list of length 2. The first element is the numeric return value for the operation, and the second element is a string value for the error. A 0 numeric error means no error in the operation.

TIMEOUT <seconds>

Terminate the operation after a given total time has elapsed.

USERPWD <username>:<password>

New in version 3.7.

Set username and password for operation.

HTTPHEADER <HTTP-header>

New in version 3.7.

HTTP header for DOWNLOAD and UPLOAD operations. HTTPHEADER can be repeated for multiple options:

file(DOWNLOAD <url>
     HTTPHEADER "Authorization: Bearer <auth-token>"
     HTTPHEADER "UserAgent: Mozilla/5.0")

NETRC <level>

New in version 3.11.

Specify whether the .netrc file is to be used for operation. If this option is not specified, the value of the CMAKE_NETRC variable will be used instead.

Valid levels are:

IGNORED

The .netrc file is ignored. This is the default.

OPTIONAL

The .netrc file is optional, and information in the URL is preferred. The file will be scanned to find which ever information is not specified in the URL.

REQUIRED

The .netrc file is required, and information in the URL is ignored.

NETRC_FILE <file>

New in version 3.11.

Specify an alternative .netrc file to the one in your home directory, if the NETRC level is OPTIONAL or REQUIRED. If this option is not specified, the value of the CMAKE_NETRC_FILE variable will be used instead.

TLS_VERIFY <ON|OFF>

Specify whether to verify the server certificate for https:// URLs. The default is to not verify. If this option is not specified, the value of the CMAKE_TLS_VERIFY variable will be used instead.

New in version 3.18: Added support to file(UPLOAD).

TLS_CAINFO <file>

Specify a custom Certificate Authority file for https:// URLs. If this option is not specified, the value of the CMAKE_TLS_CAINFO variable will be used instead.

New in version 3.18: Added support to file(UPLOAD).

For https:// URLs CMake must be built with OpenSSL support. TLS/SSL certificates are not checked by default. Set TLS_VERIFY to ON to check certificates.

Additional options to DOWNLOAD are:

EXPECTED_HASH <algorithm>=<value>

Verify that the downloaded content hash matches the expected value, where <algorithm> is one of the algorithms supported by <HASH>. If the file already exists and matches the hash, the download is skipped. If the file already exists and does not match the hash, the file is downloaded again. If after download the file does not match the hash, the operation fails with an error. It is an error to specify this option if DOWNLOAD is not given a <file>.

EXPECTED_MD5 <value>

Historical short-hand for EXPECTED_HASH MD5=<value>. It is an error to specify this if DOWNLOAD is not given a <file>.

RANGE_START <value>

New in version 3.24.

Offset of the start of the range in file in bytes. Could be omitted to download up to the specified RANGE_END.

RANGE_END <value>

New in version 3.24.

Offset of the end of the range in file in bytes. Could be omitted to download everything from the specified RANGE_START to the end of file.

Locking

file(LOCK <path> [DIRECTORY] [RELEASE] [GUARD <FUNCTION|FILE|PROCESS>] [RESULT_VARIABLE <variable>] [TIMEOUT <seconds>])

New in version 3.2.

Lock a file specified by <path> if no DIRECTORY option present and file <path>/cmake.lock otherwise. The file will be locked for the scope defined by the GUARD option (default value is PROCESS). The RELEASE option can be used to unlock the file explicitly. If the TIMEOUT option is not specified, CMake will wait until the lock succeeds or until a fatal error occurs. If TIMEOUT is set to 0, locking will be tried once and the result will be reported immediately. If TIMEOUT is not 0, CMake will try to lock the file for the period specified by the TIMEOUT <seconds> value. Any errors will be interpreted as fatal if there is no RESULT_VARIABLE option. Otherwise, the result will be stored in <variable> and will be 0 on success or an error message on failure.

Note that lock is advisory; there is no guarantee that other processes will respect this lock, i.e. lock synchronize two or more CMake instances sharing some modifiable resources. Similar logic applies to the DIRECTORY option; locking a parent directory doesn't prevent other LOCK commands from locking any child directory or file.

Trying to lock the same file twice is not allowed. Any intermediate directories and the file itself will be created if they not exist. The GUARD and TIMEOUT options are ignored on the RELEASE operation.

Archiving

file(ARCHIVE_CREATE OUTPUT <archive> PATHS <paths>... [FORMAT <format>] [COMPRESSION <compression> [COMPRESSION_LEVEL <compression-level>]] [MTIME <mtime>] [VERBOSE])

New in version 3.18.

Creates the specified <archive> file with the files and directories listed in <paths>. Note that <paths> must list actual files or directories; wildcards are not supported.

Use the FORMAT option to specify the archive format. Supported values for <format> are 7zip, gnutar, pax, paxr, raw and zip. If FORMAT is not given, the default format is paxr.

Some archive formats allow the type of compression to be specified. The 7zip and zip archive formats already imply a specific type of compression. The other formats use no compression by default, but can be directed to do so with the COMPRESSION option. Valid values for <compression> are None, BZip2, GZip, XZ, and Zstd.

New in version 3.19: The compression level can be specified with the COMPRESSION_LEVEL option. The <compression-level> should be between 0-9, with the default being 0. The COMPRESSION option must be present when COMPRESSION_LEVEL is given.

New in version 3.26: The <compression-level> of the Zstd algorithm can be set between 0-19.

Note

With FORMAT set to raw, only one file will be compressed with the compression type specified by COMPRESSION.

The VERBOSE option enables verbose output for the archive operation.

To specify the modification time recorded in tarball entries, use the MTIME option.

file(ARCHIVE_EXTRACT INPUT <archive> [DESTINATION <dir>] [PATTERNS <patterns>...] [LIST_ONLY] [VERBOSE] [TOUCH])

New in version 3.18.

Extracts or lists the content of the specified <archive>.

The directory where the content of the archive will be extracted to can be specified using the DESTINATION option. If the directory does not exist, it will be created. If DESTINATION is not given, the current binary directory will be used.

If required, you may select which files and directories to list or extract from the archive using the specified <patterns>. Wildcards are supported. If the PATTERNS option is not given, the entire archive will be listed or extracted.

LIST_ONLY will list the files in the archive rather than extract them.

Note

The working directory for this subcommand is the DESTINATION directory (provided or computed) except when LIST_ONLY is specified. Therefore, outside of script mode, it may be best to provide absolute paths to INPUT archives as they are unlikely to be extracted where a relative path works.

New in version 3.24: The TOUCH option gives extracted files a current local timestamp instead of extracting file timestamps from the archive.

With VERBOSE, the command will produce verbose output.