# file

File manipulation command.

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

    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).

    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.
`ENCODING <encoding-type>`
  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.

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(GLOB <variable>
         [LIST_DIRECTORIES true|false] [RELATIVE <path>]
         [<globbing-expressions>...])
    file(GLOB_RECURSE <variable> [FOLLOW_SYMLINKS]
         [LIST_DIRECTORIES true|false] [RELATIVE <path>]
         [<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. No specific order of results is defined other than that it is deterministic. If order is important then sort the list explicitly (e.g. using the `list(SORT)` command).

By default `GLOB` lists directories - directories are omited in result if `LIST_DIRECTORIES` is set to false.

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.

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`.

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 `OLD` then `LIST_DIRECTORIES` treats symlinks as directories.

Examples of recursive globbing include:

    /dir/*.py  - match all python files in /dir and subdirectories

    file(RENAME <oldname> <newname>)

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

    file(REMOVE [<files>...])
    file(REMOVE_RECURSE [<files>...])

Remove the given files. The `REMOVE_RECURSE` mode will remove the given files and directories, also non-empty directories. No error is emitted if a given file does not exist.

    file(MAKE_DIRECTORY [<directories>...])

Create the given directories and their parents as needed.

    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 and `/` elsewhere).

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

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

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

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>`
  Set username and password for operation.
`HTTPHEADER <HTTP-header>`
  HTTP header for operation. Suboption can be repeated several times.

Additional options to `DOWNLOAD` are:

`EXPECTED_HASH ALGO=<value>`

> Verify that the downloaded content hash matches the expected value, where `ALGO` is one of the algorithms supported by `file(<HASH>)`. If it does not match, the operation fails with an error.

`EXPECTED_MD5 <value>`
  Historical short-hand for `EXPECTED_HASH MD5=<value>`.
`TLS_VERIFY <ON|OFF>`
  Specify whether to verify the server certificate for `https://` URLs. The default is to not verify.
`TLS_CAINFO <file>`
  Specify a custom Certificate Authority file for `https://` URLs.

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 and/or use `EXPECTED_HASH` to verify downloaded content. If neither `TLS` option is given CMake will check variables `CMAKE_TLS_VERIFY` and `CMAKE_TLS_CAINFO`, respectively.

    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(GENERATE OUTPUT output-file
         <INPUT input-file|CONTENT content>
         [CONDITION expression])

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. 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.
`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.

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

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`).

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 (subject to the `CMAKE_INSTALL_MESSAGE` variable), and `NO_SOURCE_PERMISSIONS` is default. Installation scripts generated by the `install()` command use this signature (with some undocumented options for internal use).

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

Lock a file specified by `<path>` if no `DIRECTORY` option present and file `<path>/cmake.lock` otherwise. File will be locked for scope defined by `GUARD` option (default value is `PROCESS`). `RELEASE` option can be used to unlock file explicitly. If option `TIMEOUT` is not specified CMake will wait until lock succeed or until fatal error occurs. If `TIMEOUT` is set to `0` lock will be tried once and result will be reported immediately. If `TIMEOUT` is not `0` CMake will try to lock file for the period specified by `<seconds>` value. Any errors will be interpreted as fatal if there is no `RESULT_VARIABLE` option. Otherwise result will be stored in `<variable>` and will be `0` on success or 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 applied to `DIRECTORY` option - locking parent directory doesn’t prevent other `LOCK` commands to lock any child directory or file.

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