c - Why read() from a file always endwith a breakline -

test.c

int main() {     int fd = open("/test/aaa",o_rdonly);     char * str;     int len;     str = (char*)malloc(sizeof(char));     len = read(fd,str,100);     close(fd);     printf("%s\n",str);     free(str);     str = null;     return 0; } 

output like:

$echo 300 > /test/aaa $gcc test.c -o test $./test 300  $ 

why there's line break output here? there safe way ride of ? or did use read() in wrong way? thanks!

because there's newline in file see if did dump of like:

od -xcb /test/aaa 

the reason it's in file because put there: default behaviour of echo write give plus newline character.

if don't want newline character, use:

echo -n 300 >/test/aaa 

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in addition, haven't allocated enough space in malloc store other single character, might want try:

str = malloc (100); 

you'll noticed don't cast return value of malloc - it's bad habit in c, capable of implicitly casting void * returned other pointer. can hide subtle errors if explicitly cast.

it's given sizeof(char) always 1 in c don't need multiply anything.

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to honest, if want line-based file input, read wouldn't first choice. there far better options fgets doing sort of thing.