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% Document Info
\author{Gorge97}
\pdfinfo{
  /Title (c-multiprocessing-and-multithreading.pdf)
  /Creator (Cheatography)
  /Author (Gorge97)
  /Subject (C Multiprocessing \& Multithreading Cheat Sheet)
}

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\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{C Multiprocessing \& Multithreading Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Gorge97} via \textcolor{DarkBackground}{\uline{cheatography.com/154085/cs/33088/}}}
\end{tabulary}
\end{multicols}}

\fancyfoot[L]{ \footnotesize
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}Gorge97 \\
  \uline{cheatography.com/gorge97} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 10th July, 2022.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
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  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
  \SetRowColor{white}
  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
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\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Multiprocessing}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{{\bf{\#include \textless{}unistd.h\textgreater{}\{\{nl\}\} \#include \textless{}sys/types.h\textgreater{}}}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{{\bf{int fork(void)}}} \tn 
\mymulticolumn{1}{x{5.377cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Fork the current process creating a child. \{\{nl\}\}Return 0 in the child process or child ID for the parent} \tn 
% Row Count 6 (+ 4)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{{\bf{int getpid(void)}}} \tn 
\mymulticolumn{1}{x{5.377cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Return the ID of the calling process} \tn 
% Row Count 8 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{{\bf{int getppid(void)}}} \tn 
\mymulticolumn{1}{x{5.377cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Return the ID of the parent of the calling process} \tn 
% Row Count 11 (+ 3)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{{\bf{void exit(status)}}} \tn 
\mymulticolumn{1}{x{5.377cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Process termination} \tn 
% Row Count 13 (+ 2)
% Row 5
\SetRowColor{white}
\mymulticolumn{1}{x{5.377cm}}{{\bf{unlisgned int sleep(unsigned int seconds)}}} \tn 
\mymulticolumn{1}{x{5.377cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Pause the execution of the calling process for {\emph{seconds}} seconds or until a signal is received} \tn 
% Row Count 16 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Process Syncronization}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}sys/types.h\textgreater{}\{\{nl\}\} \#include \textless{}sys/wait.h\textgreater{} }}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
{\bf{pid\_t wait(*status)}} & Wait until a child process terminate the execution; \{\{nl\}\}On success return the pid of the child, on failure return -1;\{\{nl\}\} {\emph{status}} is the address of the variable cointaining the exit status \tn 
% Row Count 12 (+ 10)
% Row 2
\SetRowColor{LightBackground}
{\bf{pid\_t waitpid(pid\_t pid, int *status, int options)}} & Wait until the child specified with the {\emph{pid}} argument terminate the execution;\{\{nl\}\}{\emph{status}} is the exit status of the terminating process;\{\{nl\}\} \tn 
% Row Count 20 (+ 8)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Shared Memory}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}sys/shm.h\textgreater{}}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{int shmget(key\_t key, int size, int shmflg)}} & Create a shared memory or connec to to an existing segment; \{\{nl\}\} {\emph{key}} is a numeric key assigned to the segment. If IPC\_PRIVATE is used the segment can be only used by parent and children;\{\{nl\}\} {\emph{size}} is the size of the memory segment; {\emph{shmflg}} is a flag field: IPC\_CREATE create a new segment, IPC\_EXCL cause the command to fail if the segment already exist.\{\{nl\}\} Return the shared memory segment id or -1 if fail. \tn 
% Row Count 22 (+ 21)
% Row 2
\SetRowColor{LightBackground}
{\bf{void {\emph{shmat(int shmid, const void }}shmaddr, int shmflg)}} & Attach to the shared memory segment and return the address.\{\{nl\}\}{\emph{shmid}} is the shared memory segment id;\{\{nl\}\} {\emph{shmadr}} is the variable where the address of the segment is stored; \{\{nl\}\} {\emph{shmflg}} is used to specify the access permissions for the shared memory segment and to request special attachment conditions, such as a read-only segment. \tn 
% Row Count 40 (+ 18)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Shared Memory (cont)}}  \tn
% Row 3
\SetRowColor{LightBackground}
{\bf{int shmdt(const void *shmaddr)}} & Detaches the shared memory segment located at the address specified by shmaddr from the address space of the calling process. \tn 
% Row Count 7 (+ 7)
% Row 4
\SetRowColor{white}
{\bf{int shmctl(int shmid, int cmd, struct shmid\_ds *buf)}} & Performs the control operation specified by {\emph{cmd}} on the shared memory segment whose identifier is given in shmid. Typical usage: shmctl(shmid, IPC\_RMID, 0); Remove shared memory segment \tn 
% Row Count 17 (+ 10)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Message Queue}}  \tn
% Row 0
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\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}sys/msg.h\textgreater{} }}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{int msgget(key\_t key, int flag)}} & Creates a message queue.\{\{nl\}\} {\emph{key}} is an integer that specifies the queue key;\{\{nl\}\} {\emph{flag}} indicates creation conditions and access permissions (same as shmget).\{\{nl\}\} Return a message queue identifier or -1 in case of failure. \tn 
% Row Count 13 (+ 12)
% Row 2
\SetRowColor{LightBackground}
{\bf{int msgsnd(int msqid, const void *msgp, size\_t nbytes, int flag);}} & Send a message on the queue.\{\{nl\}\} {\emph{msqid}} is the identifier returned by msgget command; \{\{nl\}\} {\emph{msgp}} is the pointer to the message struct.\{\{nl\}\}\{\{nl\}\}{\emph{Struct msgbuf \{ \{\{nl\}\}~~long mtype; \{\{nl\}\}~~char mtext {[}TEXT LENGHT{]}; \{\{nl\}\}\};}} \{\{nl\}\}{\emph{nbytes}} is the maximum lenght of the message;\{\{nl\}\} \tn 
% Row Count 29 (+ 16)
% Row 3
\SetRowColor{white}
{\bf{int msgrcv(int msqid, void *msgp, size\_t msgsz, long msgtype, int msgflg)}} & Receive a message from the queue.\{\{nl\}\}{\emph{msqid}} corresponds to the message queue identifier;\{\{nl\}\}{\emph{msgp}} is the pointer to a message struct (the same used in msgsnd) ;\{\{nl\}\}{\emph{msgsz}} is the number of bytes to read;\{\{nl\}\}{\emph{msgtype}} is used to filterthe message in the queue. If != 0 read only a message with the same id on the queue;\{\{nl\}\}{\emph{msgflg}} is a flag that modify the behavior of the command. Using IPC\_NOWAIT return immediately of no message is found.\{\{nl\}\}The function return the number of bytes read or -1 if unsuccessful \tn 
% Row Count 56 (+ 27)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
\columnbreak
\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Message Queue (cont)}}  \tn
% Row 4
\SetRowColor{LightBackground}
{\bf{int msgctl(int msqid, int cmd, struct msqid\_ds *buf)}} & Modifies the properties of the queue or delete it. \{\{nl\}\}{\emph{msqid}} corresponds to the message queue identifier.\{\{nl\}\}\{\{nl\}\}Typical usage:\{\{nl\}\}{\emph{msgctl(msgid, IPC\_RMID, 0)}};\{\{nl\}\}Removes queue \tn 
% Row Count 10 (+ 10)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
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\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Unnamed Pipes}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}unistd.h\textgreater{}}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{int pipe( int fd{[}2{]} )}} & Creates an unnamed pipe (unidirectional).\{\{nl\}\}{\emph{fd{[}2{]}}} are two descriptor associated with the "read" end of the pipe (fd{[}0{]}) and with the "write" end of the pipe (fd{[}1{]}).\{\{nl\}\}Return 0 if the kernel could allocate enough space, -1 otherwise. \tn 
% Row Count 14 (+ 13)
% Row 2
\SetRowColor{LightBackground}
{\bf{int write (int fd, char * buf, int size)}} & The classic write function is used to write inside the buffer.\{\{nl\}\}{\emph{fd}} in this case is the descriptor of the write end of the pipe. \tn 
% Row Count 21 (+ 7)
% Row 3
\SetRowColor{white}
{\bf{int read (int fd, char * buf, int size)}} & The classic read function is user to read data from the pipe.\{\{nl\}\}{\emph{fd}} is the descriptor of the read end of the pipe. \tn 
% Row Count 27 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Named Pipes or FIFO}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}fcntl.h\textgreater{}}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{int mkfifo(const char *path, mode\_t mode);}} & Creates a named pipe (FIFO)\{\{nl\}\}{\emph{path}} corresponds to the name of the pipe;\{\{nl\}\}{\emph{mode}} corresponds to the permission mode flags. \tn 
% Row Count 8 (+ 7)
% Row 2
\SetRowColor{LightBackground}
{\bf{int open(const char *path, int flags)}} & Open the fifo defined by the name saved in {\emph{path}};\{\{nl\}\}for the {\emph{flag}} parameter use O\_WRONLY for a write only pipe or O\_EDONLY for a read only pipe. \tn 
% Row Count 16 (+ 8)
% Row 3
\SetRowColor{white}
{\bf{int write (int fd, char * buf, int size)}} & The classic write function is used to write inside the buffer.\{\{nl\}\}{\emph{fd}} in this case is the descriptor of the write end of the pipe. \tn 
% Row Count 23 (+ 7)
% Row 4
\SetRowColor{LightBackground}
{\bf{int read (int fd, char * buf, int size)}} & The classic read function is user to read data from the pipe.\{\{nl\}\}{\emph{fd}} is the descriptor of the read end of the pipe. \tn 
% Row Count 29 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Signals}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{{\bf{\#include \textless{}signal.h\textgreater{}}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{int kill(pid\_t pid, int sig)}} & Send a signal to the process indicated by the parameter pid.\{\{nl\}\}{\emph{pid}} is the pid of the process that will receive the signal;\{\{nl\}\}if set to 0 all the processes in the process group of the current process receive the signal;\{\{nl\}\}{\emph{sig}}  is the type of the signal \tn 
% Row Count 15 (+ 14)
% Row 2
\SetRowColor{LightBackground}
{\bf{sighandler\_t signal(int signum, sighandler\_t handler)}} & Installs a new signal handler for the signal with number {\emph{signum}}.\{\{nl\}\}The signal handler is set to handler which may be a user specified function or a standard function as {\bf{SIG\_IGN}} \tn 
% Row Count 25 (+ 10)
% Row 3
\SetRowColor{white}
{\bf{unsigned int alarm(unsigned int seconds)}} & Causes the system to generate a SIGALRM signal for the process after the number of real-time seconds specified by {\emph{seconds}} have elapsed. \tn 
% Row Count 32 (+ 7)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}