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Top Forums UNIX for Advanced & Expert Users Alternative to tail -n -0 -F for monitoring live log file Post 302952369 by Corona688 on Tuesday 18th of August 2015 11:18:53 AM
Old 08-18-2015
Don't do $() on an endless stream. That attempts to read all the text at once and hangs waiting. Use command | while read ...
 

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FGETLN(3)						   BSD Library Functions Manual 						 FGETLN(3)

NAME
fgetln -- get a line from a stream LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <stdio.h> char * fgetln(FILE *stream, size_t *len); DESCRIPTION
The fgetln() function returns a pointer to the next line from the stream referenced by stream. This line is not a C string as it does not end with a terminating NUL character. The length of the line, including the final newline, is stored in the memory location to which len points. (Note, however, that if the line is the last in a file that does not end in a newline, the returned text will not contain a new- line.) RETURN VALUES
Upon successful completion a pointer is returned; this pointer becomes invalid after the next I/O operation on stream (whether successful or not) or as soon as the stream is closed. Otherwise, NULL is returned. The fgetln() function does not distinguish between end-of-file and error; the routines feof(3) and ferror(3) must be used to determine which occurred. If an error occurs, the global variable errno is set to indicate the error. The end-of-file condition is remembered, even on a terminal, and all subsequent attempts to read will return NULL until the condition is cleared with clearerr(3). The text to which the returned pointer points may be modified, provided that no changes are made beyond the returned size. These changes are lost as soon as the pointer becomes invalid. ERRORS
[EBADF] The argument stream is not a stream open for reading. [ENOMEM] The internal line buffer could not be expanded due to lack of available memory, or because it would need to expand beyond INT_MAX in size. The fgetln() function may also fail and set errno for any of the errors specified for the routines fflush(3), malloc(3), read(2), stat(2), or realloc(3). SEE ALSO
ferror(3), fgets(3), fgetwln(3), fopen(3), getline(3), putc(3) HISTORY
The fgetln() function first appeared in 4.4BSD. BSD
April 19, 1994 BSD
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