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How to Compare Files In Cmake?

5 minutes read

In CMake, you can compare files using the file command with the COMPARE option. This command allows you to compare the content of two files and returns a boolean value indicating whether the files are identical or not. You can use this feature to check if a file has been modified or if two files have the same content. By comparing files in CMake, you can ensure that your build process is up-to-date and that your project is consistent across different systems.


How to compare files in cmake using the file(REMOVE_DIRECTORY)?

To compare files in CMake using the file(REMOVE_DIRECTORY) function, you would first need to create a custom command or target that compares the files by removing one of the directories and then checking if the remaining directory contains the same files as the original directory.


Here's a basic example of how you could achieve this:

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# Define the original directory
set(ORIGINAL_DIR ${CMAKE_CURRENT_SOURCE_DIR}/original)

# Define the directory to compare against
set(COMPARE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/compare)

# Create a custom target to compare the files
add_custom_target(compare_files
    COMMAND ${CMAKE_COMMAND} -E remove_directory ${COMPARE_DIR}
    COMMAND ${CMAKE_COMMAND} -E copy_directory ${ORIGINAL_DIR} ${COMPARE_DIR}
    COMMAND ${CMAKE_COMMAND} -E tar tf ${COMPARE_DIR} | sort > ${CMAKE_CURRENT_BINARY_DIR}/compare_list.txt
    COMMAND ${CMAKE_COMMAND} -E tar tf ${ORIGINAL_DIR} | sort > ${CMAKE_CURRENT_BINARY_DIR}/original_list.txt
    COMMAND diff ${CMAKE_CURRENT_BINARY_DIR}/original_list.txt ${CMAKE_CURRENT_BINARY_DIR}/compare_list.txt
    DEPENDS ${ORIGINAL_DIR}
)

# Add a custom target to compare the files before building
add_custom_target(build_all ALL DEPENDS compare_files)


In this example, the compare_files target removes the COMPARE_DIR, copies the contents of ORIGINAL_DIR to COMPARE_DIR, creates a list of files in both directories, and then uses the diff command to compare the lists of files.


You can then run cmake --build . to compare the files before building your project.


What is the difference between file(WRITE) and file(REMOVE)?

File(WRITE) is a function that is used to open a file in write mode, allowing the user to write data to the file. This function will create a new file if it does not already exist, or overwrite the existing file.


File(REMOVE) is a function used to delete a file from the file system. This function permanently removes the file from the storage device and frees up the space occupied by the file.


In summary, file(WRITE) is used to write data to a file, while file(REMOVE) is used to delete a file from the file system.


What is the difference between file(GET_HASHER) and file(LOCK)?

file(GET_HASHER) is an operation that allows a user to retrieve the hash value of a file, which is a unique identifier generated based on the contents of the file. This can be used to verify the integrity of a file or compare it with other files.


On the other hand, file(LOCK) is an operation that locks a file, preventing any other process from accessing or modifying it. This can be used to ensure exclusive access to a file, preventing conflicts and data corruption that may occur if multiple processes try to access the same file simultaneously.


What is the difference between file(CREATE_LINK) and file(DIFF)?

The difference between file(CREATE_LINK) and file(DIFF) lies in their functionality and purpose within a computer system.

  1. file(CREATE_LINK): This function is used to create a symbolic link or shortcut to a file or directory. A symbolic link is a reference to another file or directory that can be used to access the target location without having to navigate the entire file system. This allows for easier access and organization of files and directories.
  2. file(DIFF): This function is used to compare two files or directories and display the differences between them. The diff command is commonly used in Unix-like operating systems to compare text files line by line and highlight changes, deletions, and additions between the files. This is useful for identifying and resolving discrepancies in files, code, or documents.


In summary, file(CREATE_LINK) is used to create symbolic links to files or directories, while file(DIFF) is used to compare files and display the differences between them.


What is the difference between file(LOCK) and file(INSTALL)?

The term "file(LOCK)" typically refers to a temporary lock that is placed on a file to prevent other processes or users from accessing or modifying it while it is being used or edited by another process. This ensures data integrity and prevents conflicts that may arise from multiple processes trying to access the same file simultaneously.


On the other hand, "file(INSTALL)" typically refers to the process of installing a file onto a system or device. This could involve copying the file to a specific directory, setting permissions, creating shortcuts, or performing any other necessary steps to make the file usable or accessible on the system.


In summary, file(LOCK) is related to temporarily restricting access to a file for data integrity purposes, while file(INSTALL) is related to the process of placing a file onto a system or device for use.


How to compare files in cmake using the file(GLOB)?

To compare files in CMake using the file(GLOB) command, you can first use the file(GLOB) command to gather a list of files that you want to compare. Once you have the list of files, you can iterate over the list and compare each file using the file(MD5) command to calculate the MD5 hash of each file. You can then compare the MD5 hashes to determine if the files are the same.


Here is an example CMake code snippet that demonstrates how to compare files using the file(GLOB) and file(MD5) commands:

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# Get a list of files to compare
file(GLOB files_to_compare "path/to/files/*.txt")

# Iterate over the files and calculate the MD5 hash
foreach(file ${files_to_compare})
    file(MD5 file_hash ${file})
    message(STATUS "MD5 hash of ${file}: ${file_hash}")
endforeach()


In this example, replace "path/to/files/*.txt" with the path to the files you want to compare. The file(GLOB) command will retrieve a list of files that match the wildcard pattern from the specified path. The file(MD5) command is then used to calculate the MD5 hash of each file, which can be compared to determine if the files are the same.

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