qi::os

Basic OS abstracted functions.

Reference

qi::os Namespace Reference

Introduction

OS abstraction layer. qi/os.hpp . More...

Inner Definitions

Classes
Name Brief
qi::os::timeval struct similar to POSIX timeval
qi::os::ScopedThreadName Set the current thread name and restore it after use.
Functions
Name Brief
qi::os::getEnvDefault
qi::os::fopen Open a file and returns and handle on it.
qi::os::stat Get file status.
qi::os::checkdbg Check if the current process is running into a debugger.
qi::os::home Return path to the current user’s HOME.
qi::os::mktmpdir Return a writable temporary directory.
qi::os::tmp Return the system’s temporary directory.
qi::os::symlink Create a symlink from source to destination.
qi::os::gethostname Get the system’s hostname.
qi::os::isatty Test if descriptor represents a terminal.
qi::os::fnmatch Implement POSIX compliant fnmatch.
qi::os::strdup Implement POSIX compliant strdup.
qi::os::snprintf Implement POSIX compliant snprintf.
qi::os::getenv Get an environment variable.
qi::os::pathsep Get the path separator.
qi::os::setenv Change or add an environment variable.
qi::os::timezone Return the timezone.
qi::os::sleep Sleep for the specified number of seconds.
qi::os::msleep Sleep for the specified number of milliseconds.
qi::os::gettimeofday The gettimeofday() function shall obtain the current time.
qi::os::ustime Elapsed time since program started in microseconds.
qi::os::cputime Return CPU time used by the calling thread as a pair (userTime, systemTime) in microseconds.
qi::os::operator+ Add two timeval together.
qi::os::operator+ Add a delay to a timeval (in microsecond)
qi::os::operator- Substract two timeval together.
qi::os::operator- Substract a delay to a timeval (in microsecond)
qi::os::dlopen Load a dynamic library.
qi::os::dlclose Decrements the reference count on the dynamic library.
qi::os::dlsym Get the address where the symbol is loaded into memory.
qi::os::dlerror Returns a human readable string of the error code.
qi::os::spawnvp Create and execute a new process.
qi::os::spawnlp Create and execute a new process.
qi::os::system Execute a shell command.
qi::os::getpid Get the process identifier.
qi::os::gettid Get the thread identifier.
qi::os::waitpid Wait for process to change state.
qi::os::kill Send a signal to a process.
qi::os::isProcessRunning Check whether a process is running, given its file name and pid.
qi::os::findAvailablePort Find the first available port starting at port number in parameter.
qi::os::hostIPAddrs Find all network adapters and corresponding IPs.
qi::os::setCurrentThreadName Set the current thread name to the string in parameter.
qi::os::currentThreadName returns the current thread name as a std::string
qi::os::setCurrentThreadCPUAffinity Set the CPU affinity for the current thread.
qi::os::numberOfCPUs Get the number of CPUs on the local machin.
qi::os::getMachineId Returns an unique uuid for the machine.
qi::os::generateUuid Generate a universally unique identifier.
qi::os::memoryUsage Get the memory usage of a process in kB.
qi::os::getEnvParam Returns the value of the environment variableif set, the defaultVal otherwise.

Detailed Description

This module provides some functions following POSIX convention to manipulate the operating system layer in a cross-platform way.

Note

Every path taken in parameter must be encoded in UTF-8. Every path returned is encoded in UTF-8.

Functions

FILE* qi::os::fopen(const char* filename, const char* mode)

Brief: Open a file and returns and handle on it.

Parameters:
  • filename – Path to the file (in UTF-8).
  • mode – The mode.
Returns:

A FILE* handle if successful, 0 on error.

Nothing special under POSIX systems, it’s only useful for Windows, where files should be open using a widestring.

Refer to man 3 fopen for more informations on POSIX systems, and to the documentation of _wfopen on MSDN to understand the Windows behaviors.

New in version 1.12.

int qi::os::stat(const char* filename, struct stat* pstat)

Brief: Get file status.

Parameters:
  • filename – Path to the file (in UTF-8).
  • pstat – A pointer to a stat structure that will be filled by the function.
Returns:

0 on success, -1 on error

Stats the file pointed to by filename and fills in pstat. You need to include <sys/stat.h> to get access to struct.

New in version 1.12.

int qi::os::checkdbg()

Brief: Check if the current process is running into a debugger.

Returns:-1 on error, 1 if debugger is present, 0 otherwise
std::string qi::os::home()

Brief: Return path to the current user’s HOME.

Returns:String to user’s HOME
std::string qi::os::mktmpdir(const char* prefix = "")

Brief: Return a writable temporary directory.

Parameters:
  • prefix – Prefix of the tmp file (in UTF-8).
Returns:

The path to the temporary directory.

The caller is responsible for destroying the returned directory. This will create a unique directory in the temporary directory returned by qi::os::tmp().

The specified prefix will be prepended to a uniquely generated name.

New in version 1.12.1.

std::string qi::os::tmp()

Brief: Return the system’s temporary directory.

Returns:The path to the system’s temporary directory.

The directory is writable and exists. The caller is responsible for destroying the temporary files it creates.

void qi::os::symlink(const qi::Path& source, const qi::Path& destination)

Create a symlink from source to destination.

std::string qi::os::gethostname()

Brief: Get the system’s hostname.

Returns:The system’s hostname. An empty string is returned on failure.
int qi::os::isatty(int fd = 1)

Brief: Test if descriptor represents a terminal.

Parameters:
  • fd – File descriptor.
Returns:

Returns a value of 1 if the given file descriptor is a terminal. Otherwise returns a value of 0. By default test for stdout (1).

New in version 1.22.

bool qi::os::fnmatch(const std::string& pattern, const std::string& string)

Implement POSIX compliant fnmatch.

char* qi::os::strdup(const char* src)

Implement POSIX compliant strdup.

int qi::os::snprintf(char* str, size_t size, const char* format, ...)

See also

http://en.cppreference.com/w/cpp/io/c/fprintf

std::string qi::os::getenv(const char* var)

Brief: Get an environment variable.

Parameters:
  • var – The environment variable to search for.
Returns:

The value in the environment, or an empty string if there is no match.

Searches the environment list to find the environment variable var, and returns a pointer to the corresponding value string.

New in version 1.12.

std::string qi::os::pathsep()

Brief: Get the path separator.

Returns:The separator of paths.

It is the separator we can found in PATH env for example.

int qi::os::setenv(const char* var, const char* value)

Brief: Change or add an environment variable.

Parameters:
  • var – The variable name.
  • value – The value of the variable.
Returns:

0 on success, or -1 on error.

Adds the variable name to the environment with the value in argument if name does not already exist. Else changes its value.

New in version 1.12.

std::string qi::os::timezone()

Brief: Return the timezone.

Returns:A string with the timezone.

New in version 1.22.

void qi::os::sleep(unsigned int seconds)

Brief: Sleep for the specified number of seconds.

Parameters:
  • seconds – Number of seconds to sleep.

Under Linux/OS X it will not be disturbed by eventual signals. Makes the calling thread sleep until seconds have elapsed or a signal arrives which is not ignored.

See also

qi::os::msleep(unsigned int)

New in version 1.12.

void qi::os::msleep(unsigned int milliseconds)

Brief: Sleep for the specified number of milliseconds.

Parameters:
  • milliseconds – Number of milliseconds to sleep.

Under Linux/OSX it will not be disturbed by eventual signals sent to process. Makes the calling thread sleep until millliseconds have elapsed or a signal which is not ignored arrives.

See also

qi::os::sleep(unsigned int)

New in version 1.12.

int qi::os::gettimeofday(qi::os::timeval* tp)

Brief: The gettimeofday() function shall obtain the current time.

Parameters:
  • tp – The timeval structure used to return the current time.
Returns:

0 on success

Deprecatedsince 2.4. Use qi::SystemClock::now() instead.

The gettimeofday() function shall obtain the current time, expressed as seconds and microseconds since the Epoch, and store it in the timeval structure pointed to by tp. The resolution of the system clock is unspecified. This clock is subject to NTP adjustments.

qi::int64_t qi::os::ustime()

Brief: Elapsed time since program started in microseconds.

Returns:Return qi::int64_t in microseconds.
std::pair<int64_t, int64_t> qi::os::cputime()

Brief: Return CPU time used by the calling thread as a pair (userTime, systemTime) in microseconds.

Returns:Return pair(userTime, systemTime) in microseconds.
qi::os::timeval qi::os::operator+(const qi::os::timeval& lhs, const qi::os::timeval& rhs)

Brief: Add two timeval together.

Parameters:
  • lhs – First timeval
  • rhs – Second timeval
qi::os::timeval qi::os::operator+(const qi::os::timeval& lhs, long us)

Brief: Add a delay to a timeval (in microsecond)

Parameters:
  • lhs – Frist timeval
  • us – Second timeval
qi::os::timeval qi::os::operator-(const qi::os::timeval& lhs, const qi::os::timeval& rhs)

Brief: Substract two timeval together.

Parameters:
  • lhs – First timeval
  • rhs – Second timeval
qi::os::timeval qi::os::operator-(const qi::os::timeval& lhs, long us)

Brief: Substract a delay to a timeval (in microsecond)

Parameters:
  • lhs – Frist timeval
  • us – Second timeval
void* qi::os::dlopen(const char* filename, int flag = -1)

Brief: Load a dynamic library.

Parameters:
  • filename – Name of the dynamic library.
  • flag – Flags used to load the dynamic library.
Returns:

A handle to the library, or 0 on error.

Loads the dynamic library file named by the null-terminated string filename and returns an opaque “handle” for the dynamic library. If filename is NULL, then the returned handle is for the main program.

No flag is supported on windows platform. Otherwise, see man 0p dlfcn.h for more information on flags available. If not given, RTLD_NOW is used.

See also

qi::os::dlerror() for more details on the error.

New in version 1.12.

int qi::os::dlclose(void* handle)

Brief: Decrements the reference count on the dynamic library.

Parameters:
  • handle – The dynamic library handle.
Returns:

This function returns 0 on success, and non-zero on error.

Decrements the reference count on the dynamic library handle. If the reference count drops to zero and no other loaded library uses symbols in it, then the dynamic library is unloaded.

If there is an error you can look which one with dlerror function provided in this same module.

See also

qi::os::dlerror() for more details on the error.

New in version 1.12.

void* qi::os::dlsym(void* handle, const char* symbol)

Brief: Get the address where the symbol is loaded into memory.

Parameters:
  • handle – Handle on a dynamic library returned by dlopen().
  • symbol – The null-terminated symbol name.
Returns:

The address of the symbol, or 0 on error.

If the symbol is not found in the specified library or any of the libraries that were automatically loaded by qi::os::dlopen() when that library was loaded, qi::os::dlsym() returns 0.

See also

qi::os::dlerror() for more details on the error.

New in version 1.12.

const char* qi::os::dlerror()

Brief: Returns a human readable string of the error code.

Returns:NULL if no error has occurred since it was last called. An human readable string otherwise.

Warning

On windows, return value may be modified by another function unrelated to qi::os::dlopen familly. This function does not ensure that error value is 0 at initialisation. You may reset error value before a call to any qi::os::dl{open, sym, close} functions with a first call to this function.

Returns a human readable string describing the most recent error that occurred from qi::os::dlopen(const char*, int), qi::os::dlsym(void*, const char*) or qi::os::dlclose(void*) since the last call to qi::os::dlerror().

New in version 1.12.

int qi::os::spawnvp(char* const argv[])

Brief: Create and execute a new process.

Parameters:
  • argv – The command line arguments of the new process as an array (NULL terminated).
Returns:

-1 on error, child pid otherwise.

Creates and executes a new process.

New in version 1.12.

int qi::os::spawnlp(const char* argv, ...)

Brief: Create and execute a new process.

Parameters:
  • argv – Path to the file to be executed.
  • ... – The command line arguments of the new process as var args.
Returns:

-1 on error, child pid otherwise.

Creates and executes a new process.

New in version 1.12.

int qi::os::system(const char* command)

Brief: Execute a shell command.

Parameters:
  • command – Command to execute.
Returns:

The value returned is -1 on error, and the return status of the command otherwise.

Executes a command by calling /bin/sh -c command, and returns when the command has completed.

New in version 1.12.

int qi::os::getpid()

Get the process identifier.

int qi::os::gettid()

Get the thread identifier.

int qi::os::waitpid(int pid, int* status)

Brief: Wait for process to change state.

Parameters:
  • pid – Pid to wait.
  • status – Status returned by the process.
Returns:

See detailed description.

Suspends execution of the calling process until a child specified by pid argument changes of state.

Return values (rc):

  • rc = 0 means that everything went well.
  • rc > 0 means that an error occurred. (For instance, no process corresponding to the pid was found). The exact value is an errno code.
  • rc < 0 means that the child was killed by a signal. The value of the signal is -rc.

New in version 1.12.

int qi::os::kill(int pid, int sig)

Brief: Send a signal to a process.

Parameters:
  • pid – PID to kill.
  • sig – Signal to deliver to the process.
Returns:

See detailed description.

The kill() function shall send a signal to a process or a group of processes specified by pid.

Return value (rc):

  • rc = 0 means that everything went well.
  • rc != 0 means that an error occurred. (For instance, no process corresponding to the pid was found).

New in version 1.14.

bool qi::os::isProcessRunning(int pid, const std::string& fileName = std::string()

Brief: Check whether a process is running, given its file name and pid.

Parameters:
  • pid – The PID to check.
  • fileName – The name of the process: the executable file name with no .exe or _d.exe extension.
Returns:

true if the process is running and has the expected name.

unsigned short int qi::os::findAvailablePort(unsigned short int port)

Brief: Find the first available port starting at port number in parameter.

Parameters:
  • port – First port tested, then each port following it is tested one by one until one available is found.
Returns:

Available port or 0 on error

Warning

This function is not thread safe and suffers from a race condition. You should avoid calling it and call listen on port 0 instead. This will pick a random port with no race condition.

New in version 1.14.

std::map<std::string, std::vector<std::string>> qi::os::hostIPAddrs(bool ipv6Addr = false)

Brief: Find all network adapters and corresponding IPs.

Parameters:
  • ipv6Addr – Look for IPv6 addresses instead of IPv4 ones.
Returns:

A map of interfaces associated with the list of IPs of that interface.

New in version 1.14.

void qi::os::setCurrentThreadName(const std::string& name)

Brief: Set the current thread name to the string in parameter.

Parameters:
  • name – The new name of the current thread.

Prefer using ScopedThreadName that will restore the thread name on exit.

std::string qi::os::currentThreadName()

Brief: returns the current thread name as a std::string

Returns:a std::string of at most 16 characters
bool qi::os::setCurrentThreadCPUAffinity(const std::vector<int>& cpus)

Brief: Set the CPU affinity for the current thread.

Parameters:
  • cpus – a vector of CPU core ids
Returns:

true on success

When CPU Affinity is set, the current thread will only be allowed to run on the given set of cores.

New in version 1.22.

long qi::os::numberOfCPUs()

Brief: Get the number of CPUs on the local machin.

Returns:Number of CPUs
std::string qi::os::getMachineId()

Brief: Returns an unique uuid for the machine.

Returns:The uuid of the machine.

The UUID is stored on disk and will stay unchanged as long as it is not removed. All programs running on the same machine will have the same UUID returned. An empty string is returned on failure.

std::string qi::os::generateUuid()

Brief: Generate a universally unique identifier.

Returns:The uuid. .. versionadded:: 1.20
size_t qi::os::memoryUsage(unsigned int pid)

Brief: Get the memory usage of a process in kB.

Parameters:
  • pid – PID of a process
Returns:

Returns a value > 0 corresponding to the memory in RAM used by the process in kB. Otherwise returns a value of 0, meaning that it was impossible to get the memory usage.

template<typename T>

Brief: Returns the value of the environment variableif set, the defaultVal otherwise.

Parameters:
  • name -- Name of the environment variable
  • defaultVal -- DefaultVal to return if the environment variable isn't set.
Returns:

Function obtains the current value of the environment variable, name if set. Return defaultVal otherwise. .. versionadded:: 2.4

T qi::os::getEnvParam(const char* name, T defaultVal)
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