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Top Forums UNIX for Dummies Questions & Answers need to read 3° character from a text file Post 78832 by vgersh99 on Friday 22nd of July 2005 08:38:34 AM
Old 07-22-2005
Quote:
Originally Posted by vgersh99
echo 12345 | sed 's/^.\{3\}\(.\).*/\1/'
Code:
^        - from the beginning of the line
.\{3\}  - any 3 characters
\(.\)    - capture one character [the 4-th chars from the beginning]
.*       - any number of characters

\1       - print the first 'capture'

 

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PCAP_SETNONBLOCK(3PCAP) 												   PCAP_SETNONBLOCK(3PCAP)

NAME
pcap_setnonblock, pcap_getnonblock - set or get the state of non-blocking mode on a capture device SYNOPSIS
#include <pcap/pcap.h> char errbuf[PCAP_ERRBUF_SIZE]; int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf); int pcap_getnonblock(pcap_t *p, char *errbuf); DESCRIPTION
pcap_setnonblock() puts a capture handle into ``non-blocking'' mode, or takes it out of ``non-blocking'' mode, depending on whether the nonblock argument is non-zero or zero. It has no effect on ``savefiles''. If there is an error, -1 is returned and errbuf is filled in with an appropriate error message; otherwise, 0 is returned. In ``non-blocking'' mode, an attempt to read from the capture descriptor with pcap_dispatch() will, if no packets are currently available to be read, return 0 immediately rather than blocking waiting for packets to arrive. pcap_loop() and pcap_next() will not work in ``non-blocking'' mode. When first activated with pcap_activate() or opened with pcap_open_live() , a capture handle is not in ``non-blocking mode''; a call to pcap_setnonblock() is required in order to put it into ``non-blocking'' mode. RETURN VALUE
pcap_getnonblock() returns the current ``non-blocking'' state of the capture descriptor; it always returns 0 on ``savefiles''. If there is an error, -1 is returned and errbuf is filled in with an appropriate error message. errbuf is assumed to be able to hold at least PCAP_ERRBUF_SIZE chars. SEE ALSO
pcap(3PCAP), pcap_loop(3PCAP), pcap_next_ex(3PCAP), pcap_geterr(3PCAP) 18 October 2014 PCAP_SETNONBLOCK(3PCAP)
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