---
name: "pvm_trecv"
section: "3"
platform: "linux"
package: "pvm-dev"
version: "3.4.2-8"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/pvm_trecv"
---

# pvm\_trecv(3)

Receive with timeout.

## NAME

pvm\_trecv - Receive with timeout.

## SYNOPSIS

```
C	#include <sys/time.h>
	int bufid = pvm_trecv( int tid, int msgtag, struct timeval *tmout )
Fortran	call pvmftrecv( tid, msgtag, sec, usec, bufid )
```

## PARAMETERS

- tid

  **Integer to match task identifier of sending process.**\

- msgtag

  **Integer to match message tag;** **should be \>= 0.**\

- tmout

  **(or** *sec* and *usec*) Time to wait before returning without a message.\

- bufid

  Integer returns the value of the new active receive buffer identifier. Values less than zero indicate an error.

## DESCRIPTION

The routine *pvm\_trecv* blocks the process until a message with label *msgtag* has arrived from *tid*. pvm\_trecv then places the message in a new *active* receive buffer, also clearing the current receive buffer. If no matching message arrives within the specified waiting time, pvm\_trecv returns without a message.

A -1 in *msgtag* or *tid* matches anything. This allows the user the following options. If *tid* = -1 then pvm\_trecv will accept a message from any process which has a matching *msgtag*. If *msgtag* = -1 then pvm\_trecv will accept any message that is sent from process *tid*. If *tid* and *msgtag* are both -1, then pvm\_trecv will accept any message from any process.

In C, the *tmout* fields tv\_sec and tv\_usec specify how long pvm\_trecv will wait without returning a matching message. In Fortran, two separate parameters, *sec* and *usec* are passed. With both set to zero, pvm\_trecv behaves the same as *pvm\_nrecv*, which is to probe for messages and return immediately even if none are matched. In C, passing a null pointer in *tmout* makes pvm\_trecv act like *pvm\_recv*, that is, it will wait indefinitely. In Fortran, setting *sec* to -1 has the same effect.

The PVM model guarantees the following about message order. If task 1 sends message A to task 2, then task 1 sends message B to task 2, message A will arrive at task 2 before message B. Moreover, if both messages arrive before task 2 does a receive, then a wildcard receive will always return message A.

If pvm\_trecv is successful, *bufid* will be the new active receive buffer identifier. If no message is received, pvm\_trecv returns 0. If some error occurs then *bufid* will be \< 0.

Once pvm\_trecv returns, the data in the message can be unpacked into the user's memory using the unpack routines.

## EXAMPLES

```
C:
	struct timeval tmout;
	tid = pvm_parent();
	msgtag = 4 ;
	tmout.tv_sec = 60;
	tmout.tv_usec = 0;
	if ((bufid = pvm_trecv( tid, msgtag, &tmout )) > 0) {
		pvm_upkint( tid_array, 10, 1 );
		pvm_upkint( problem_size, 1, 1 );
		pvm_upkfloat( input_array, 100, 1 );
	}

Fortran:
	CALL PVMFTRECV( -1, 4, 60, 0, BUFID )
	IF (BUFID .EQ. 0) GO TO 666
	CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
	CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
666	CONTINUE
```

## ERRORS

These error conditions can be returned by *pvm\_trecv*

- PvmBadParam

  giving an invalid tid value, or msgtag \< -1.

- PvmSysErr

  pvmd not responding.

## SEE ALSO

pvm\_bufinfo(3PVM), pvm\_getminfo(3PVM), pvm\_nrecv(3PVM), pvm\_recv(3PVM), pvm\_unpack(3PVM), pvm\_probe(3PVM), pvm\_send(3PVM), pvm\_mcast(3PVM)