The Linux Programming Interface

Pipes and FIFOs 917 Figure 44-8: Deadlock between processes opening two FIFOs Nonblocking read() and write() The O_NONBLOCK flag ...

918 Chapter 44 The impact of the O_NONBLOCK flag when writing to a pipe or FIFO is made complex by interactions with the PIPE_BU ...

Pipes and FIFOs 919 When using pipes, we must be careful to close unused descriptors in order to ensure that reading processes d ...

920 Chapter 44 array.) Obtaining the correct process ID from this structure will allow pclose() to select the child upon which t ...

Chapter 45: Introduction to System V IPC...................................................................... System V IPC is t ...

922 Chapter 45 together, first appearing in the late 1970s in Columbus UNIX. This was a Bell-internal UNIX implementation used f ...

Introduction to System V IPC 923 Creating and opening a System V IPC object Each System V IPC mechanism has an associated get sy ...

924 Chapter 45 If no IPC object corresponding to the given key currently exists, and IPC_CREAT (analogous to the open() O_CREAT ...

Introduction to System V IPC 925 45.2 IPC Keys System V IPC keys are integer values represented using the data type key_t. The I ...

926 Chapter 45 This key value is generated from the supplied pathname and proj value using an implementation-defined algorithm. ...

Introduction to System V IPC 927 id = msgget(key, IPC_CREAT | S_IRUSR | S_IWUSR); if (id == -1) errExit("msgget"); 45.3 Associat ...

928 Chapter 45 in the get system call used to create the object, but can be changed subsequently using the IPC_SET operation. As ...

Introduction to System V IPC 929 An attempt by the second user to obtain an identifier for this message queue using the followin ...

930 Chapter 45 Suppose a client engages in an extended dialogue with a server, with multiple IPC operations being performed by e ...

Introduction to System V IPC 931 /* While msgget() fails, try creating the queue exclusively */ while ((msqid = msgget(key, IPC_ ...

932 Chapter 45 the kernel maintains an associated ipc_ids structure that records various global information about all instances ...

Introduction to System V IPC 933 The identifier for the IPC object is calculated using the following formula: identifier = ind ...

934 Chapter 45 45.6 The ipcs and ipcrm Commands The ipcs and ipcrm commands are the System V IPC analogs of the ls and rm file c ...

Introduction to System V IPC 935 45.7 Obtaining a List of All IPC Objects Linux provides two nonstandard methods of obtaining a ...

936 Chapter 45 On Linux, the ipcs –l command can be used to list the limits on each of the IPC mechanisms. Programs can employ t ...