134 lines
2.7 KiB
Groff
134 lines
2.7 KiB
Groff
.\" $Id: getnetent.3,v 8.2 1996/05/09 05:59:10 vixie Exp $
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.TH getnetent 3
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.SH NAME
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getnetent, getnetbyaddr, getnetbyname, setnetent, endnetent \- get networks
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entry
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.SH SYNTAX
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.nf
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.B #include <netdb.h>
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.PP
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.B struct netent *getnetent()
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.PP
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.B struct netent *getnetbyname(\fIname\fP)
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.B char *\fIname\fP;
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.PP
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.B struct netent *getnetbyaddr(\fInet\fP, \fItype\fP)
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.B unsigned long \fInet\fP; int \fItype\fP;
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.PP
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.B void setnetent(\fIstayopen\fP)
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.B int \fIstayopen\fP;
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.PP
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.B void endnetent()
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.fi
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.SH DESCRIPTION
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The
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.IR getnetent ,
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.IR getnetbyname ,
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and
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.I getnetbyaddr
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subroutines
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each return a pointer to an object with the
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following structure
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containing the broken-out
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fields of a line in the
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.I networks
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database.
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.RS
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.PP
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.nf
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struct netent {
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char *n_name; /* official name of net */
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char **n_aliases; /* alias list */
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int n_addrtype; /* net number type */
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long n_net; /* net number */
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};
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.ft R
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.ad
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.fi
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.RE
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.PP
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The members of this structure are:
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.TP \w'n_addrtype'u+2n
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n_name
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The official name of the network.
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.TP \w'n_addrtype'u+2n
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n_aliases
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A zero terminated list of alternate names for the network.
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.TP \w'n_addrtype'u+2n
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n_addrtype
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The type of the network number returned: AF_INET.
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.TP \w'n_addrtype'u+2n
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n_net
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The network number. Network numbers are returned in machine byte
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order.
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.PP
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If the
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.I stayopen
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flag on a
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.I setnetent
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subroutine is NULL, the
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.I networks
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database is opened. Otherwise the
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.I setnetent
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has the effect of rewinding the
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.I networks
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database.
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The
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.I endnetent
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may be called to
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close the
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.I networks
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database when processing is complete.
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.PP
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The
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.I getnetent
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subroutine simply reads the next
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line while
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.I getnetbyname
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and
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.I getnetbyaddr
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search until a matching
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.I name
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or
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.I net
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number is found
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(or until EOF is encountered). The \fItype\fP must be AF_INET.
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The
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.I getnetent
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subroutine keeps a pointer in the database, allowing
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successive calls to be used
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to search the entire file.
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.PP
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A call to
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.I setnetent
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must be made before a
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.I while
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loop using
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.I getnetent
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in order to perform initialization and an
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.I endnetent
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must be used after the loop. Both
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.I getnetbyname
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and
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.I getnetbyaddr
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make calls to
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.I setnetent
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and
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.I endnetent .
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.SH FILES
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.I /etc/networks
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.SH DIAGNOSTICS
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Null pointer (0) returned on EOF or error.
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.SH SEE ALSO
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.nf
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networks(5)
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RFC 1101
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.SH HISTORY
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The getnetent(), getnetbyaddr(), getnetbyname(), setnetent(), and
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endnetent() functions appeared in 4.2BSD.
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.SH BUGS
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The data space used by these functions is static; if future use requires the
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data, it should be copied before any subsequent calls to these functions
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overwrite it. Only Internet network numbers are currently understood.
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Expecting network numbers to fit in no more than 32 bits is probably naive.
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