open

Open a file in the specified mode.

    
    
    
open(filename)

    
    
    
open(filename, mode)

Examples

Create a file, write data, then read it.

    javascript
    
    
function main() {
    let fileHandle = os.open("output.txt", "w+")
    if (!fileHandle) {
        Log("Failed to open file")
        return
    }
    let bytesWritten = fileHandle.write("Hello FMZ!")
    Log("Bytes written:", bytesWritten)     // Bytes written: 10
    fileHandle.seek(0, 0)
    let fileContent = fileHandle.read()
    Log("File content read:", fileContent)  // File content read: Hello FMZ!
    fileHandle.close()
}

Returns

Arguments

See Also

Remarks

File opening modes:

• r : read (read-only, file must exist)

• w : write (write-only, creates file if it doesn't exist, clears content if it exists)

• a : append (append write, creates file if it doesn't exist, writes to the end if it exists)

• + : Adding + after r/w/a means both read and write are allowed (e.g., "r+", "w+", "a+")

• b : binary (binary mode, commonly used in Windows to distinguish text/binary files, e.g., "rb", "wb")

Files are opened/created in the files folder under the live trading database file directory (xxx.db3, where xxx is the live trading Id).

fgets

Read the entire file content at once.

    
    
    
fgets(filename)

Examples

Read the content of a configuration file.

    javascript
    
    
function main() {
    // 先创建、写入文件
    // let fileHandle = os.open("config.json", "w+")
    // if (!fileHandle) {
    //     Log("Failed to open file")
    //     return
    // }
    // let objJson = {"name": "tom", "age": 18}
    // fileHandle.write(JSON.stringify(objJson))
    // fileHandle.close()

    let content = os.fgets("config.json")
    Log("Config content:", content)  // Config content: {"name":"tom","age":18}
}

Returns

Arguments

See Also

Remarks

Suitable for quick reading of small files, loading the entire file content into memory at once.

If the file does not exist, the fgets() function will throw an error: InternalError: failed to open file: openat config.json: no such file or directory at main.

fputs

Write content to a file.

    
    
    
fputs(filename, content)

    
    
    
fputs(filename, content, append)

Examples

Save strategy configuration to file.

    javascript
    
    
function main() {
    let config = '{"strategy": "MA", "period": 20}'
    let bytesWritten = os.fputs("strategy_config.json", config)
    Log("Bytes written:", bytesWritten)                                          // Bytes written: 32
    Log(`os.fgets("strategy_config.json"):`, os.fgets("strategy_config.json"))   // os.fgets("strategy_config.json"): {"strategy": "MA", "period": 20}

    // 追加日志信息
    let logInfo = "\n[" + new Date().toISOString() + "] Config saved"
    os.fputs("strategy_config.json", logInfo, true)
    Log(`os.fgets("strategy_config.json"):`, os.fgets("strategy_config.json"))   // os.fgets("strategy_config.json"): {"strategy": "MA", "period": 20} [2025-09-08T07:20:30.563Z] Config saved
}

Returns

Arguments

See Also

Remarks

Convenient file writing method, overwrites file content by default. Set append to true to append to the end of the file.

mmap

Memory-mapped file, returns the binary data of the file.

    
    
    
mmap(filename)

Examples

Map the binary data of a file.

    javascript
    
    
function ab2str(buf) {
    let arr = new Uint8Array(buf)
    return String.fromCharCode.apply(null, arr)
}

function main() {
    let buffer = os.mmap("strategyConfig/testData.txt")
    Log("File size in bytes:", buffer.byteLength)
    let arr = Array.from(new Uint8Array(buffer))
    Log("arr:",  arr)                        // arr: [72,101,108,108,111,32,70,77,90,33]
    Log("ab2str(buffer):", ab2str(buffer))   // ab2str(buffer): Hello FMZ!
}

Returns

Arguments

See Also

Remarks

Suitable for efficient reading and processing of large files, maps the file into memory and returns it as an ArrayBuffer.

getRootDir

Get the root directory path for file operations.

    
    
    
getRootDir()

Examples

Get and display the root directory path.

    javascript
    
    
function main() {
    let rootDir = os.getRootDir()
    Log("Root directory:", rootDir)
}

Returns

See Also

listFiles

List files and subdirectories in the specified directory.

    
    
    
listFiles()

    
    
    
listFiles(pattern)

Examples

List matched files and directories.

    javascript
    
    
function main() {
    // 列出所有json文件
    let result = os.listFiles("*.json")
    Log("result:", result)

    // 列出所有内容
    let allFiles = os.listFiles()
    Log("allFiles:", allFiles)
}

Returns

Arguments

See Also

Remarks

When pattern parameter is not specified, lists all files and subdirectories in the current directory (../files).

exists

Check if the specified file or directory exists.

    
    
    
exists(filename)

Examples

Check if a file or path exists.

    javascript
    
    
function main() {
    Log(`os.exists("./strategyConfig"):`, os.exists("./strategyConfig"))    // os.exists("./strategyConfig"): true
    Log(`os.exists("./strategyConfig/testData.txt"):`, os.exists("./strategyConfig/testData.txt"))  // os.exists("./strategyConfig/testData.txt"): true
    // Log(`os.exists("/strategyConfig"):`, os.exists("/strategyConfig"))   // InternalError: invalid filename: path traversal or absolute path not allowed at main
    Log(`os.exists("test_1.txt"):`, os.exists("test_1.txt"))                // os.exists("test_1.txt"): true
    Log(`os.exists("test_2.txt"):`, os.exists("test_2.txt"))                // os.exists("test_2.txt"): false
}

Returns

Arguments

See Also

remove

Delete the specified file.

    
    
    
remove(filename)

Examples

Example of deleting a file.

    javascript
    
    
function main() {
    let tempFile = "test_1.txt"
    if (os.exists(tempFile)) {
        let success = os.remove(tempFile)
        Log("Temp file deleted:", success)
    }
}

Returns

Arguments

See Also

Remarks

This function is only for deleting files, not for deleting directories. To delete directories, please use the rmdir() function.

mkdir

Create a directory.

    
    
    
mkdir(dirname)

Examples

Create a data storage directory, create a file and write data.

    javascript
    
    
function main() {
    let success = os.mkdir("data/backtest/results")
    Log("Directory created:", success)

    if (success) {
        os.fputs("data/backtest/results/summary.txt", "Backtest completed")
    }
}

Returns

Arguments

See Also

Remarks

Supports recursive creation of multi-level directories. If parent directories do not exist, they will be created automatically.

rmdir

Remove a directory and all its contents.

    
    
    
rmdir(dirname)

Examples

Remove a directory and all its contents.

    javascript
    
    
function main() {
    let tempDir = "data"
    if (os.exists(tempDir)) {
        let success = os.rmdir(tempDir)
        Log("directory removed:", success)
    }
}

Returns

Arguments

See Also

Remarks

This operation will permanently delete the directory and all its contents, please use with caution.

rename

Rename a file or move a file.

    
    
    
rename(oldName, newName)

Examples

Rename a file and move it to another directory.

    javascript
    
    
function main() {
    let oldFileName = "output.txt"
    let newFileName = "outputFiles/" + new Date().getTime() + "output.txt"
    // let retRename = os.rename(oldFileName, newFileName)
    // Log("retRename:", retRename)  // InternalError: failed to rename file: renameat output.txt outputFiles/1757322073139output.txt: no such file or directory at main

    os.mkdir("outputFiles")
    let retRename = os.rename(oldFileName, newFileName)
    Log("retRename:", retRename)     // retRename: true
}

Returns

Arguments

See Also

Remarks

This function can be used to rename a file or move a file to another directory. If the directory of the new path does not exist, the operation will fail.

stat

Get detailed statistics information of a file.

    
    
    
stat(filename)

Examples

Get file information and check file size.

    javascript
    
    
function main() {
    if (os.exists("strategyConfig/testData.txt")) {
        let stat = os.stat("strategyConfig/testData.txt")  // stat: {"size":10,"mode":420,"mtime":1757312981796,"atime":1757312981796,"ctime":1757312981796}
        Log("stat:", stat)
    }
}

Returns

Arguments

See Also

Remarks

The returned FileStat object contains the following fields:

• size: File size.

• mode: File permissions.

• mtime: Last modification time.

• atime: Last access time.

• ctime: Creation time.

exit

Exit the program.

    
    
    
exit()

    
    
    
exit(status)

Examples

Exit program after checking conditions.

    javascript
    
    
function main() {
    if (!os.exists("required_config.json")) {
        Log("Required configuration file not found!")
        os.exit(1)  // Abnormal exit
    }
    Log("Configuration found, continuing...")
    // Normal strategy logic...
}

Returns

Arguments

See Also

Remarks

Immediately terminates program execution. Status code 0 indicates normal exit, non-zero values indicate abnormal exit (will be displayed as error in live trading).