--- name: "stropts.h" section: "0p" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/stropts.h" --- # stropts.h(0p) STREAMS interface (STREAMS) ## PROLOG This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. ## NAME stropts.h — STREAMS interface (**STREAMS**) ## SYNOPSIS ``` #include ``` ## DESCRIPTION The *\* header shall define the **bandinfo** structure, which shall include at least the following members: ``` int bi_flag Flushing type. unsigned char bi_pri Priority band. ``` The *\* header shall define the **strpeek** structure, which shall include at least the following members: ``` struct strbuf ctlbuf The control portion of the message. struct strbuf databuf The data portion of the message. t_uscalar_t flags RS_HIPRI or 0. ``` The *\* header shall define the **strbuf** structure, which shall include at least the following members: ``` char *buf Pointer to buffer. int len Length of data. int maxlen Maximum buffer length. ``` The *\* header shall define the **strfdinsert** structure, which shall include at least the following members: ``` struct strbuf ctlbuf The control portion of the message. struct strbuf databuf The data portion of the message. int fildes File descriptor of the other STREAM. t_uscalar_t flags RS_HIPRI or 0. int offset Relative location of the stored value. ``` The *\* header shall define the **strioctl** structure, which shall include at least the following members: ``` int ic_cmd ioctl() command. char *ic_dp Pointer to buffer. int ic_len Length of data. int ic_timout Timeout for response. ``` The *\* header shall define the **strrecvfd** structure, which shall include at least the following members: ``` int fd Received file descriptor. gid_t gid GID of sender. uid_t uid UID of sender. ``` The *\* header shall define the **uid\_t** and **gid\_t** types through **typedef**, as described in *\*. The *\* header shall define the **t\_scalar\_t** and **t\_uscalar\_t** types, respectively, as signed and unsigned opaque types of equal length of at least 32 bits. The *\* header shall define the **str\_list** structure, which shall include at least the following members: ``` struct str_mlist *sl_modlist STREAMS module names. int sl_nmods Number of STREAMS module names. ``` The *\* header shall define the **str\_mlist** structure, which shall include at least the following member: ``` char l_name[FMNAMESZ+1] A STREAMS module name. ``` The *\* header shall define at least the following symbolic constants for use as the *request* argument to *ioctl*(): - I\_ATMARK Is the top message \`\`marked''? - I\_CANPUT Is a band writable? - I\_CKBAND See if any messages exist in a band. - I\_FDINSERT Send implementation-defined information about another STREAM. - I\_FIND Look for a STREAMS module. - I\_FLUSH Flush a STREAM. - I\_FLUSHBAND Flush one band of a STREAM. - I\_GETBAND Get the band of the top message on a STREAM. - I\_GETCLTIME Get close time delay. - I\_GETSIG Retrieve current notification signals. - I\_GRDOPT Get the read mode. - I\_GWROPT Get the write mode. - I\_LINK Connect two STREAMs. - I\_LIST Get all the module names on a STREAM. - I\_LOOK Get the top module name. - I\_NREAD Size the top message. - I\_PEEK Peek at the top message on a STREAM. - I\_PLINK Persistently connect two STREAMs. - I\_POP Pop a STREAMS module. - I\_PUNLINK Dismantle a persistent STREAMS link. - I\_PUSH Push a STREAMS module. - I\_RECVFD Get a file descriptor sent via I\_SENDFD. - I\_SENDFD Pass a file descriptor through a STREAMS pipe. - I\_SETCLTIME Set close time delay. - I\_SETSIG Ask for notification signals. - I\_SRDOPT Set the read mode. - I\_STR Send a STREAMS *ioctl*(). - I\_SWROPT Set the write mode. - I\_UNLINK Disconnect two STREAMs. The *\* header shall define at least the following symbolic constant for use with I\_LOOK: - FMNAMESZ The minimum size in bytes of the buffer referred to by the *arg* argument. The *\* header shall define at least the following symbolic constants for use with I\_FLUSH: - FLUSHR Flush read queues. - FLUSHRW Flush read and write queues. - FLUSHW Flush write queues. The *\* header shall define at least the following symbolic constants for use with I\_SETSIG: - S\_BANDURG When used in conjunction with S\_RDBAND, SIGURG is generated instead of SIGPOLL when a priority message reaches the front of the STREAM head read queue. - S\_ERROR Notification of an error condition reaches the STREAM head. - S\_HANGUP Notification of a hangup reaches the STREAM head. - S\_HIPRI A high-priority message is present on a STREAM head read queue. - S\_INPUT A message, other than a high-priority message, has arrived at the head of a STREAM head read queue. - S\_MSG A STREAMS signal message that contains the SIGPOLL signal reaches the front of the STREAM head read queue. - S\_OUTPUT The write queue for normal data (priority band 0) just below the STREAM head is no longer full. This notifies the process that there is room on the queue for sending (or writing) normal data downstream. - S\_RDBAND A message with a non-zero priority band has arrived at the head of a STREAM head read queue. - S\_RDNORM A normal (priority band set to 0) message has arrived at the head of a STREAM head read queue. - S\_WRBAND The write queue for a non-zero priority band just below the STREAM head is no longer full. - S\_WRNORM Equivalent to S\_OUTPUT. The *\* header shall define at least the following symbolic constant for use with I\_PEEK: - RS\_HIPRI Only look for high-priority messages. The *\* header shall define at least the following symbolic constants for use with I\_SRDOPT: - RMSGD Message-discard mode. - RMSGN Message-non-discard mode. - RNORM Byte-STREAM mode, the default. - RPROTDAT Deliver the control part of a message as data when a process issues a *read*(). - RPROTDIS Discard the control part of a message, delivering any data part, when a process issues a *read*(). - RPROTNORM Fail *read*() with **\[EBADMSG\]** if a message containing a control part is at the front of the STREAM head read queue. The *\* header shall define at least the following symbolic constant for use with I\_SWOPT: - SNDZERO Send a zero-length message downstream when a *write*() of 0 bytes occurs. The *\* header shall define at least the following symbolic constants for use with I\_ATMARK: - ANYMARK Check if the message is marked. - LASTMARK Check if the message is the last one marked on the queue. The *\* header shall define at least the following symbolic constant for use with I\_UNLINK: - MUXID\_ALL Unlink all STREAMs linked to the STREAM associated with *fildes*. The *\* header shall define the following symbolic constants for *getmsg*(), *getpmsg*(), *putmsg*(), and *putpmsg*(): - MORECTL More control information is left in message. - MOREDATA More data is left in message. - MSG\_ANY Receive any message. - MSG\_BAND Receive message from specified band. - MSG\_HIPRI Send/receive high-priority message. The *\* header may make visible all of the symbols from *\*. The *\* header may also define macros for message types using names that start with *M\_*. The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. ``` int fattach(int, const char *); int fdetach(const char *); int getmsg(int, struct strbuf *restrict, struct strbuf *restrict, int *restrict); int getpmsg(int, struct strbuf *restrict, struct strbuf *restrict, int *restrict, int *restrict); int ioctl(int, int, ...); int isastream(int); int putmsg(int, const struct strbuf *, const struct strbuf *, int); int putpmsg(int, const struct strbuf *, const struct strbuf *, int, int); ``` *The following sections are informative.* ## APPLICATION USAGE None. ## RATIONALE None. ## FUTURE DIRECTIONS None. ## SEE ALSO ***\***, ***\*** The System Interfaces volume of POSIX.1‐2017, *close()*, *fattach()*, *fcntl()*, *fdetach()*, *getmsg()*, *ioctl()*, *isastream()*, *open()*, *pipe()*, *read()*, *poll()*, *putmsg()*, *signal()*, *write()* ## COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .