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Top Forums Shell Programming and Scripting Read line from serial device with BASH Post 302984917 by RudiC on Wednesday 2nd of November 2016 03:34:56 PM
Old 11-02-2016
The cursor blinks as the read didn't stop as it didn't receive a <newline> char. I guess your device sends <carriage return>s? Try
Code:
read -d $'\r' INPUT </dev/ttyACM0

For testing, you might want to experiment with other read options:
Quote:
-n nchars
read returns after reading nchars characters rather than waiting for a complete line of input, but honor a delimiter if fewer than nchars characters are
read before the delimiter.
-N nchars
read returns after reading exactly nchars characters rather than waiting for a complete line of input, unless EOF is encountered or read times out.
.
.
.
-t timeout
Cause read to time out and return failure if a complete line of input (or a specified number of characters) is not read within timeout seconds. timeout
may be a decimal number with a fractional portion following the decimal point.
 

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PCAP_NEXT_EX(3) 					     Library Functions Manual						   PCAP_NEXT_EX(3)

NAME
pcap_next_ex, pcap_next - read the next packet from a pcap_t SYNOPSIS
#include <pcap/pcap.h> int pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header, const u_char **pkt_data); const u_char *pcap_next(pcap_t *p, struct pcap_pkthdr *h); DESCRIPTION
pcap_next_ex() reads the next packet and returns a success/failure indication. If the packet was read without problems, the pointer pointed to by the pkt_header argument is set to point to the pcap_pkthdr struct for the packet, and the pointer pointed to by the pkt_data argument is set to point to the data in the packet. pcap_next() reads the next packet (by calling pcap_dispatch() with a cnt of 1) and returns a u_char pointer to the data in that packet. The pcap_pkthdr structure pointed to by h is filled in with the appropriate values for the packet. RETURN VALUE
pcap_next_ex() returns 1 if the packet was read without problems, 0 if packets are being read from a live capture, and the timeout expired, -1 if an error occurred while reading the packet, and -2 if packets are being read from a ``savefile'', and there are no more packets to read from the savefile. If -1 is returned, pcap_geterr() or pcap_perror() may be called with p as an argument to fetch or display the error text. pcap_next() returns a pointer to the packet data on success, and returns NULL if an error occured, or if no packets were read from a live capture (if, for example, they were discarded because they didn't pass the packet filter, or if, on platforms that support a read timeout that starts before any packets arrive, the timeout expires before any packets arrive, or if the file descriptor for the capture device is in non-blocking mode and no packets were available to be read), or if no more packets are available in a ``savefile.'' Unfortunately, there is no way to determine whether an error occured or not. SEE ALSO
pcap(3), pcap_geterr(3), pcap_dispatch(3) 5 April 2008 PCAP_NEXT_EX(3)
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