In the  image there is a RCS -Tree which have  following parts:

One Branch : 1.3.1.1  and this branch is originated from 1.3

Two releases : 1.x.x.x and 2.x

##########- STEPS FOR BRANCHING IN THE RCS TREE -#############

–>>    In already existing rcs tree, check the revisions by
using ‘rlog filename.c,v‘ .

–>>    Chose a revision to branch , and check-out its editable
             version.
i.e,
co -l1.3 filename.c,v

–>>    Now make changes into the file and check it in the tree
with  the particular branch Number,
i.e,
ci -r1.3.1 filename.c

–>>    Hence it will create first revision of branch 1.3.1
i.e,
version- 1.3.1.1    (1st Rev. of branch 1.3.1)

–>>    You also can create New Release for your Project, simply
by using Release No.
i.e,
ci -r2 filename.c

–>>    Hence it will create Second revision of RCS-Tree
i.e,
version- 2.1    (1st Rev. of Release 2)

–>>    You should refer to the above image while reading this for better
           understanding.

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But we can change this behaviour by using fcntl() funtion as follows;

fcntl(rfd, F_SETFL, O_NONBLOCK);

Here,

rfd =Read File Descriptor given by pipe() call,

F_SETFL = It tells fcntl() what to do with rfd,

O_NONBLOCK = Set the read flags associated with rfd so as to perfrom Non-Block Read.

Here’s also another way which is ‘pipe2()’ system call. Which quite easy