find length of a fixed width file wtih a little twist - linux

Question

Hi Wonderful People/My Gurus and all kind-hearted people.
I've a fixed width file and currently i'm trying to find the length of those rows that contain x bytes. I tried couple of awk commands but, it is not giving me the result that i wanted. My fixed width contains 208bytes, but there are few rows that don't contain 208 bytes. I"m trying to discover those records that doesn't have 208bytes.
this cmd gave me the file length
awk '{print length;exit}' file.text
here i tried to print rows that contain 101 bytes, but it didn't work.
awk '{print length==101}' file.text
Any help/insights here would be highly helpful

Answer 1

With awk:
awk 'length() < 208' file
Well, length() gives you the number of characters, not bytes. This number can differ in unicode context. You can use the LANG environment variable to force awk to use bytes:
LANG=C awk 'length() < 208' file

Answer 2

Perl to the rescue!
perl -lne 'print "$.:", length if length != 208' -- file.text
-n reads the input line by line
-l removes newlines from the input before processing it and adds them to print
The one-liner will print line number ($.) and the length of the line for each line whose length is different than 208.

Answer 3

if you're using gawk, then it's no issue, even in typical UTF-8 locale mode :
length(s) = # chars native to locale,
# typically that means # utf-8 chars
match(s, /$/) - 1 = # raw bytes # this also work for pure-binary
# inputs, without triggering
# any error messages in gawk Unicode mode
Best illustrated by example :
0000000 3347498554 3381184647 3182945161 171608122
: Ɔ ** LJ ** Ȉ ** ɉ ** 㷽 ** ** : 210 : \n
072 306 206 307 207 310 210 311 211 343 267 275 072 210 072 012
: ? 86 ? 87 ? 88 ? 89 ? ? ? : 88 : nl
58 198 134 199 135 200 136 201 137 227 183 189 58 136 58 10
3a c6 86 c7 87 c8 88 c9 89 e3 b7 bd 3a 88 3a 0a
0000020
# gawk profile, created Sat Oct 29 20:32:49 2022
BEGIN {
1 __ = "\306\206\307\207\310" (_="\210") \
"\311\211\343\267\275"
1 print "",__,_
1 STDERR = "/dev/stderr"
1 print ( match(_, /$/) - 1, "_" ) > STDERR # *A
1 print ( length(__), match(__, /$/) - 1 ) > STDERR # *B
1 print ( (__~_), match(__, (_) ".*") ) > STDERR # *C
1 print ( RSTART, RLENGTH ) > STDERR # *D
}
1 | _ *A # of bytes off "_" because it was defined as 0x88 \210
5 | 11 *B # of chars of "__", and
# of bytes of it :
# 4 x 2-byte UC
# + 1 x 3-byte UC = 11
1 | 3 *C # does byte \210 exist among larger string (true/1),
# and which unicode character is 1st to
# contain \210 - the 3rd one, by original definition
3 | 3 *D # notice I also added a ".*" to the tail of this match() :
# if the left-side string being tested is valid UTF-8,
# then this will match all the way to the end of string,
# inclusive, in which you can deduce :
#
# "\210 first appeared in 3rd-to-last utf-8 character"
Combining that inferred understanding :
RLENGTH = "3 chars to the end, inclusive",
with knowledge of how many to its left :
RSTART - 1 = "2 chars before",
yields a total count of 3 + 2 = 5, affirming length()'s result