CODEWITHSUNDEEP
linuxc
Aruna Hewapathirane
Aruna Hewapathirane

Reputation: 95

linux netlink struct member definition

I recently came across this while browsing the Linux kernel source:

struct netlink_kernel_cfg cfg = {
    .input  = scsi_nl_rcv_msg,
    .groups = SCSI_NL_GRP_CNT,
};

The full source is here.

I am trying to understand how the member definitions .input and .groups work? The C structs I am familiar with are similar to:

struct employee{
       char    name[30];
       int     empId;
       float   salary;
};

So how do .input and .groups work?

Upvotes: 2

Views: 267

Answers (1)

Stephen Kitt
Stephen Kitt

Reputation: 2881

As mosvy said in a comment, these are C99 designated initialisers.

struct netlink_kernel_cfg cfg = {
    .input  = scsi_nl_rcv_msg,
    .groups = SCSI_NL_GRP_CNT,
};

doesn’t declare a structure (as your employee example does), it declares a variable, cfg, of type struct netlink_kernel_cfg, and initialises two of its members, input and groups.

The main advantages of this syntax are that the declaration order no longer matters, that members can be omitted (and are initialised in the same way as static variables), and that it’s easier to read.

Upvotes: 3

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