OS module in Node.js

Node.js / August 24, 2020 / TopCode / 0

Introduction

In this blog post, we will learn how can you use Node.js core module to get os specific Information. In the early days of JavaScript, it was just a client-side language but after the introduction of Node.js, it has become a server-side language as well. If you are building your web application by using Node.js then getting system-related information is a common programming practice. Node.js built-in OS module provides methods and properties to get operation system-related information. You don’t need any third-party module to get this type of information.

OS module

To use os module first you need to import os module as follows:

const os = require('os')

Let’s see main APIs of os module.

1. os.arch() : This method returns the operating system CPU architecture for which the Node.js binary was compiled. Possible values are  x64, arm, arm64.
2. os.cpus(): This method returns information about each logical CPU core on your system.
3. os.freemem(): This method returns the number of bytes that represent the free memory in the system.
4. os.homedir(): This method returns the current user’s home directory.
5. os.hostname(): This method returns the host name of the operating system as a string.
6. os.networkInterfaces(): This method returns details of the network interfaces available on the system.
7. os.platform(): This method returns a string identifying the operating system platform. The value is set at compile time. Possible values are 'aix', 'darwin', 'freebsd', 'linux', 'openbsd', 'sunos', and 'win32'
8. os.release(): This method returns a string which denotes the operating system release number
9. os.tempdir(): This method returns the operating system’s default directory for temporary files as a string
10. os.totalmem(): This method returns total avaliable memory on the system in bytes.
11. os.uptime(): This method returns the system uptime in seconds.
12. os.userInfo(): This method returns an object that contains the current username, uid, gid, homedir and shell.

Along with APIs os module also provides some properties as follows:

• os.EOL: gives the line delimiter sequence. It’s \n on Posix, and \r\n on Windows.
• os.constants: The following constants are exported by os.constants.

Constant	Description
SIGHUP	Sent to indicate when a controlling terminal is closed or a parent process exits.
SIGINT	Sent to indicate when a user wishes to interrupt a process (Ctrl+C).
SIGQUIT	Sent to indicate when a user wishes to terminate a process and perform a core dump.
SIGILL	Sent to a process to notify that it has attempted to perform an illegal, malformed, unknown, or privileged instruction.
SIGTRAP	Sent to a process when an exception has occurred.
SIGABRT	Sent to a process to request that it abort.
SIGIOT	Synonym for SIGABRT
SIGBUS	Sent to a process to notify that it has caused a bus error.
SIGFPE	Sent to a process to notify that it has performed an illegal arithmetic operation.
SIGKILL	Sent to a process to terminate it immediately.
SIGUSR1 SIGUSR2	Sent to a process to identify user-defined conditions.
SIGSEGV	Sent to a process to notify of a segmentation fault.
SIGPIPE	Sent to a process when it has attempted to write to a disconnected pipe.
SIGALRM	Sent to a process when a system timer elapses.
SIGTERM	Sent to a process to request termination.
SIGCHLD	Sent to a process when a child process terminates.
SIGSTKFLT	Sent to a process to indicate a stack fault on a coprocessor.
SIGCONT	Sent to instruct the operating system to continue a paused process.
SIGSTOP	Sent to instruct the operating system to halt a process.
SIGTSTP	Sent to a process to request it to stop.
SIGBREAK	Sent to indicate when a user wishes to interrupt a process.
SIGTTIN	Sent to a process when it reads from the TTY while in the background.
SIGTTOU	Sent to a process when it writes to the TTY while in the background.
SIGURG	Sent to a process when a socket has urgent data to read.
SIGXCPU	Sent to a process when it has exceeded its limit on CPU usage.
SIGXFSZ	Sent to a process when it grows a file larger than the maximum allowed.
SIGVTALRM	Sent to a process when a virtual timer has elapsed.
SIGPROF	Sent to a process when a system timer has elapsed.
SIGWINCH	Sent to a process when the controlling terminal has changed its size.
SIGIO	Sent to a process when I/O is available.
SIGPOLL	Synonym for SIGIO
SIGLOST	Sent to a process when a file lock has been lost.
SIGPWR	Sent to a process to notify of a power failure.
SIGINFO	Synonym for SIGPWR
SIGSYS	Sent to a process to notify of a bad argument.
SIGUNUSED	Synonym for SIGSYS

All constants will not be available on every operating system.

The following error constants are exported by os.constants.errno.

POSIX error constants

Constant	Description
E2BIG	Denotes that the list of arguments is longer than expected.
EACCES	Denotes that the operation did not have sufficient permissions.
EADDRINUSE	Denotes that the network address is already in use.
EADDRNOTAVAIL	Denotes that the network address is currently unavailable for use.
EAFNOSUPPORT	Denotes that the network address family is not supported.
EAGAIN	Denotes that there is no data available and to try the operation again later.
EALREADY	Denotes that the socket already has a pending connection in progress.
EBADF	Denotes that a file descriptor is not valid.
EBADMSG	Denotes an invalid data message.
EBUSY	Denotes that a device or resource is busy.
ECANCELED	Denotes that an operation was canceled.
ECHILD	Denotes that there are no child processes.
ECONNABORTED	Denotes that the network connection has been aborted.
ECONNREFUSED	Denotes that the network connection has been refused.
ECONNRESET	Denotes that the network connection has been reset.
EDEADLK	Denotes that a resource deadlock has been avoided.
EDESTADDRREQ	Denotes that a destination address is required.
EDOM	Denotes that an argument is out of the domain of the function.
EDQUOT	Denotes that the disk quota has been exceeded.
EEXIST	Denotes that the file already exists.
EFAULT	Denotes an invalid pointer address.
EFBIG	Denotes that the file is too large.
EHOSTUNREACH	Denotes that the host is unreachable.
EIDRM	Denotes that the identifier has been removed.
EILSEQ	Denotes an illegal byte sequence.
EINPROGRESS	Denotes that an operation is already in progress.
EINTR	Denotes that a function call was interrupted.
EINVAL	Denotes that an invalid argument was provided.
EIO	Denotes an otherwise unspecified I/O error.
EISCONN	Denotes that the socket is connected.
EISDIR	Denotes that the path is a directory.
ELOOP	Denotes too many levels of symbolic links in a path.
EMFILE	Denotes that there are too many open files.
EMLINK	Denotes that there are too many hard links to a file.
EMSGSIZE	Denotes that the provided message is too long.
EMULTIHOP	Denotes that a multihop was attempted.
ENAMETOOLONG	Denotes that the filename is too long.
ENETDOWN	Denotes that the network is down.
ENETRESET	Denotes that the connection has been aborted by the network.
ENETUNREACH	Denotes that the network is unreachable.
ENFILE	Denotes too many open files in the system.
ENOBUFS	Denotes that no buffer space is available.
ENODATA	Denotes that no message is available on the stream head to read queue.
ENODEV	Denotes that there is no such device.
ENOENT	Denotes that there is no such file or directory.
ENOEXEC	Denotes an exec format error.
ENOLCK	Denotes that there are no locks available.
ENOLINK	Denotes that a link has been severed.
ENOMEM	Denotes that there is not enough space.
ENOMSG	Denotes that there is no message of the desired type.
ENOPROTOOPT	Denotes that a given protocol is not available.
ENOSPC	Denotes that there is no space available on the device.
ENOSR	Denotes that there are no stream resources available.
ENOSTR	Denotes that a given resource is not a stream.
ENOSYS	Denotes that a function has not been implemented.
ENOTCONN	Denotes that the socket is not connected.
ENOTDIR	Denotes that the path is not a directory.
ENOTEMPTY	Denotes that the directory is not empty.
ENOTSOCK	Denotes that the given item is not a socket.
ENOTSUP	Denotes that a given operation is not supported.
ENOTTY	Denotes an inappropriate I/O control operation.
ENXIO	Denotes no such device or address.
EOPNOTSUPP	Denotes that an operation is not supported on the socket. Although ENOTSUP and EOPNOTSUPP have the same value on Linux, according to POSIX.1 these error values should be distinct.)
EOVERFLOW	Denotes that a value is too large to be stored in a given data type.
EPERM	Denotes that the operation is not permitted.
EPIPE	Denotes a broken pipe.
EPROTO	Denotes a protocol error.
EPROTONOSUPPORT	Denotes that a protocol is not supported.
EPROTOTYPE	Denotes the wrong type of protocol for a socket.
ERANGE	Denotes that the results are too large.
EROFS	Denotes that the file system is read only.
ESPIPE	Denotes an invalid seek operation.
ESRCH	Denotes that there is no such process.
ESTALE	Denotes that the file handle is stale.
ETIME	Denotes an expired timer.
ETIMEDOUT	Denotes that the connection timed out.
ETXTBSY	Denotes that a text file is busy.
EWOULDBLOCK	Denotes that the operation would block.
EXDEV	Denotes an improper link.

Windows-specific error constants

The following error codes are specific to the Windows operating system.

Constant	Description
WSAEINTR	Denotes an interrupted function call.
WSAEBADF	Denotes an invalid file handle.
WSAEACCES	Denotes insufficient permissions to complete the operation.
WSAEFAULT	Denotes an invalid pointer address.
WSAEINVAL	Denotes that an invalid argument was passed.
WSAEMFILE	Denotes that there are too many open files.
WSAEWOULDBLOCK	Denotes that a resource is temporarily unavailable.
WSAEINPROGRESS	Denotes that an operation is currently in progress.
WSAEALREADY	Denotes that an operation is already in progress.
WSAENOTSOCK	Denotes that the resource is not a socket.
WSAEDESTADDRREQ	Denotes that a destination address is required.
WSAEMSGSIZE	Denotes that the message size is too long.
WSAEPROTOTYPE	Denotes the wrong protocol type for the socket.
WSAENOPROTOOPT	Denotes a bad protocol option.
WSAEPROTONOSUPPORT	Denotes that the protocol is not supported.
WSAESOCKTNOSUPPORT	Denotes that the socket type is not supported.
WSAEOPNOTSUPP	Denotes that the operation is not supported.
WSAEPFNOSUPPORT	Denotes that the protocol family is not supported.
WSAEAFNOSUPPORT	Denotes that the address family is not supported.
WSAEADDRINUSE	Denotes that the network address is already in use.
WSAEADDRNOTAVAIL	Denotes that the network address is not available.
WSAENETDOWN	Denotes that the network is down.
WSAENETUNREACH	Denotes that the network is unreachable.
WSAENETRESET	Denotes that the network connection has been reset.
WSAECONNABORTED	Denotes that the connection has been aborted.
WSAECONNRESET	Denotes that the connection has been reset by the peer.
WSAENOBUFS	Denotes that there is no buffer space available.
WSAEISCONN	Denotes that the socket is already connected.
WSAENOTCONN	Denotes that the socket is not connected.
WSAESHUTDOWN	Denotes that data cannot be sent after the socket has been shut down.
WSAETOOMANYREFS	Denotes that there are too many references.
WSAETIMEDOUT	Denotes that the connection has timed out.
WSAECONNREFUSED	Denotes that the connection has been refused.
WSAELOOP	Denotes that a name cannot be translated.
WSAENAMETOOLONG	Denotes that a name was too long.
WSAEHOSTDOWN	Denotes that a network host is down.
WSAEHOSTUNREACH	Denotes that there is no route to a network host.
WSAENOTEMPTY	Denotes that the directory is not empty.
WSAEPROCLIM	Denotes that there are too many processes.
WSAEUSERS	Denotes that the user quota has been exceeded.
WSAEDQUOT	Denotes that the disk quota has been exceeded.
WSAESTALE	Denotes a stale file handle reference.
WSAEREMOTE	Denotes that the item is remote.
WSASYSNOTREADY	Denotes that the network subsystem is not ready.
WSAVERNOTSUPPORTED	Indicates that the winsock.dll version is out of range.
WSANOTINITIALISED	Denotes that successful WSAStartup has not yet been performed.
WSAEDISCON	Denotes that a graceful shutdown is in progress.
WSAENOMORE	Denotes that there are no more results.
WSAECANCELLED	Denotes that an operation has been canceled.
WSAEINVALIDPROCTABLE	Denotes that the procedure call table is invalid.
WSAEINVALIDPROVIDER	Denotes an invalid service provider.
WSAEPROVIDERFAILEDINIT	Denotes that the service provider failed to initialize.
WSASYSCALLFAILURE	Denotes a system call failure.
WSASERVICE_NOT_FOUND	Denotes that a service was not found.
WSATYPE_NOT_FOUND	Denotes that a class type was not found.
WSA_E_NO_MORE	Denotes that there are no more results.
WSA_E_CANCELLED	Denotes that the call was canceled.
WSAEREFUSED	Denotes that a database query was refused.

dlopen constants

If available on the operating system, the following constants are exported in os.constants.dlopen. See dlopen(3) for detailed information.

Constant	Description
RTLD_LAZY	Perform lazy binding. Node.js sets this flag by default.
RTLD_NOW	Resolve all undefined symbols in the library before dlopen(3) returns.
RTLD_GLOBAL	Symbols defined by the library will be made available for symbol resolution of subsequently loaded libraries.
RTLD_LOCAL	The converse of RTLD_GLOBAL. This is the default behavior if neither flag is specified.
RTLD_DEEPBIND	Make a self-contained library use its own symbols in preference to symbols from previously loaded libraries.

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