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Full Discussion: Another binary manipulation thread.
Top Forums UNIX for Advanced & Expert Users Another binary manipulation thread. Post 302851081 by DGPickett on Friday 6th of September 2013 05:05:08 PM
Old 09-06-2013
Wel, in a null terminated string application, null is always '' the empty string, as it reterminates the string, just as a strcpy of a 5 byte plus null string into a 20 byte buffer initialized with 19 spaces and a null creates a string length of 5.

Now, is it the only character that is equal to '' the empty string? Does read differentiate that from EOF in a while read loop?
Code:
$ bash -c 'export ct=0 ; unset IFS ; all256|while read -rn 1 c
do
 echo "$(( ct++ )): '"'"'$c'"'"'"
done|cat -vt'
0: ''
1: '^A'
2: '^B'
3: '^C'
4: '^D'
5: '^E'
6: '^F'
7: '^G'
8: '^H'
9: ''
10: ''
11: '^K'
12: '^L'
13: '^M'
14: '^N'
15: '^O'
16: '^P'
17: '^Q'
18: '^R'
19: '^S'
20: '^T'
21: '^U'
22: '^V'
23: '^W'
24: '^X'
25: '^Y'
26: '^Z'
27: '^['
28: '^\'
29: '^]'
30: '^^'
31: '^_'
32: ''
33: '!'
34: '"'
35: '#'
36: '$'
37: '%'
38: '&'
39: '''
40: '('
41: ')'
42: '*'
43: '+'
44: ','
45: '-'
46: '.'
47: '/'
48: '0'
49: '1'
50: '2'
51: '3'
52: '4'
53: '5'
54: '6'
55: '7'
56: '8'
57: '9'
58: ':'
59: ';'
60: '<'
61: '='
62: '>'
63: '?'
64: '@'
65: 'A'
66: 'B'
67: 'C'
68: 'D'
69: 'E'
70: 'F'
71: 'G'
72: 'H'
73: 'I'
74: 'J'
75: 'K'
76: 'L'
77: 'M'
78: 'N'
79: 'O'
80: 'P'
81: 'Q'
82: 'R'
83: 'S'
84: 'T'
85: 'U'
86: 'V'
87: 'W'
88: 'X'
89: 'Y'
90: 'Z'
91: '['
92: '\'
93: ']'
94: '^'
95: '_'
96: '`'
97: 'a'
98: 'b'
99: 'c'
100: 'd'
101: 'e'
102: 'f'
103: 'g'
104: 'h'
105: 'i'
106: 'j'
107: 'k'
108: 'l'
109: 'm'
110: 'n'
111: 'o'
112: 'p'
113: 'q'
114: 'r'
115: 's'
116: 't'
117: 'u'
118: 'v'
119: 'w'
120: 'x'
121: 'y'
122: 'z'
123: '{'
124: '|'
125: '}'
126: '~'
127: '^?'
128: 'M-^@'
129: 'M-^A'
130: 'M-^B'
131: 'M-^C'
132: 'M-^D'
133: 'M-^E'
134: 'M-^F'
135: 'M-^G'
136: 'M-^H'
137: 'M-^I'
138: 'M-
'
139: 'M-^K'
140: 'M-^L'
141: 'M-^M'
142: 'M-^N'
143: 'M-^O'
144: 'M-^P'
145: 'M-^Q'
146: 'M-^R'
147: 'M-^S'
148: 'M-^T'
149: 'M-^U'
150: 'M-^V'
151: 'M-^W'
152: 'M-^X'
153: 'M-^Y'
154: 'M-^Z'
155: 'M-^['
156: 'M-^\'
157: 'M-^]'
158: 'M-^^'
159: 'M-^_'
160: 'M- '
161: 'M-!'
162: 'M-"'
163: 'M-#'
164: 'M-$'
165: 'M-%'
166: 'M-&'
167: 'M-''
168: 'M-('
169: 'M-)'
170: 'M-*'
171: 'M-+'
172: 'M-,'
173: 'M--'
174: 'M-.'
175: 'M-/'
176: 'M-0'
177: 'M-1'
178: 'M-2'
179: 'M-3'
180: 'M-4'
181: 'M-5'
182: 'M-6'
183: 'M-7'
184: 'M-8'
185: 'M-9'
186: 'M-:'
187: 'M-;'
188: 'M-<'
189: 'M-='
190: 'M->'
191: 'M-?'
192: 'M-@'
193: 'M-A'
194: 'M-B'
195: 'M-C'
196: 'M-D'
197: 'M-E'
198: 'M-F'
199: 'M-G'
200: 'M-H'
201: 'M-I'
202: 'M-J'
203: 'M-K'
204: 'M-L'
205: 'M-M'
206: 'M-N'
207: 'M-O'
208: 'M-P'
209: 'M-Q'
210: 'M-R'
211: 'M-S'
212: 'M-T'
213: 'M-U'
214: 'M-V'
215: 'M-W'
216: 'M-X'
217: 'M-Y'
218: 'M-Z'
219: 'M-['
220: 'M-\'
221: 'M-]'
222: 'M-^'
223: 'M-_'
224: 'M-`'
225: 'M-a'
226: 'M-b'
227: 'M-c'
228: 'M-d'
229: 'M-e'
230: 'M-f'
231: 'M-g'
232: 'M-h'
233: 'M-i'
234: 'M-j'
235: 'M-k'
236: 'M-l'
237: 'M-m'
238: 'M-n'
239: 'M-o'
240: 'M-p'
241: 'M-q'
242: 'M-r'
243: 'M-s'
244: 'M-t'
245: 'M-u'
246: 'M-v'
247: 'M-w'
248: 'M-x'
249: 'M-y'
250: 'M-z'
251: 'M-{'
252: 'M-|'
253: 'M-}'
254: 'M-~'
255: 'M-^?'
$

Too many aliases. Whatever is or defaults to IFS is indistinguishable from null:
Code:
$ bash -c 'export ct=0 IFS="
" ; all256|while read -ern 1 c
do
 echo "$(( ct++ )): '"'"'$c'"'"'"
done|cat -vt'
0: ''
1: '^A'
2: '^B'
3: '^C'
4: '^D'
5: '^E'
6: '^F'
7: '^G'
8: '^H'
9: '^I'
10: ''
11: '^K'
12: '^L'
13: '^M'
14: '^N'
15: '^O'
16: '^P'
17: '^Q'
18: '^R'
19: '^S'
20: '^T'
21: '^U'
22: '^V'
23: '^W'
24: '^X'
25: '^Y'
26: '^Z'
27: '^['
28: '^\'
29: '^]'
30: '^^'
31: '^_'
32: ' '
33: '!'
34: '"'
35: '#'
36: '$'
37: '%'
38: '&'
39: '''
40: '('
41: ')'
42: '*'
43: '+'
44: ','
45: '-'
46: '.'
47: '/'
48: '0'
49: '1'
50: '2'
51: '3'
52: '4'
53: '5'
54: '6'
55: '7'
56: '8'
57: '9'
58: ':'
59: ';'
60: '<'
61: '='
62: '>'
63: '?'
64: '@'
65: 'A'
66: 'B'
67: 'C'
68: 'D'
69: 'E'
70: 'F'
71: 'G'
72: 'H'
73: 'I'
74: 'J'
75: 'K'
76: 'L'
77: 'M'
78: 'N'
79: 'O'
80: 'P'
81: 'Q'
82: 'R'
83: 'S'
84: 'T'
85: 'U'
86: 'V'
87: 'W'
88: 'X'
89: 'Y'
90: 'Z'
91: '['
92: '\'
93: ']'
94: '^'
95: '_'
96: '`'
97: 'a'
98: 'b'
99: 'c'
100: 'd'
101: 'e'
102: 'f'
103: 'g'
104: 'h'
105: 'i'
106: 'j'
107: 'k'
108: 'l'
109: 'm'
110: 'n'
111: 'o'
112: 'p'
113: 'q'
114: 'r'
115: 's'
116: 't'
117: 'u'
118: 'v'
119: 'w'
120: 'x'
121: 'y'
122: 'z'
123: '{'
124: '|'
125: '}'
126: '~'
127: '^?'
128: 'M-^@'
129: 'M-^A'
130: 'M-^B'
131: 'M-^C'
132: 'M-^D'
133: 'M-^E'
134: 'M-^F'
135: 'M-^G'
136: 'M-^H'
137: 'M-^I'
138: 'M-
'
139: 'M-^K'
140: 'M-^L'
141: 'M-^M'
142: 'M-^N'
143: 'M-^O'
144: 'M-^P'
145: 'M-^Q'
146: 'M-^R'
147: 'M-^S'
148: 'M-^T'
149: 'M-^U'
150: 'M-^V'
151: 'M-^W'
152: 'M-^X'
153: 'M-^Y'
154: 'M-^Z'
155: 'M-^['
156: 'M-^\'
157: 'M-^]'
158: 'M-^^'
159: 'M-^_'
160: 'M- '
161: 'M-!'
162: 'M-"'
163: 'M-#'
164: 'M-$'
165: 'M-%'
166: 'M-&'
167: 'M-''
168: 'M-('
169: 'M-)'
170: 'M-*'
171: 'M-+'
172: 'M-,'
173: 'M--'
174: 'M-.'
175: 'M-/'
176: 'M-0'
177: 'M-1'
178: 'M-2'
179: 'M-3'
180: 'M-4'
181: 'M-5'
182: 'M-6'
183: 'M-7'
184: 'M-8'
185: 'M-9'
186: 'M-:'
187: 'M-;'
188: 'M-<'
189: 'M-='
190: 'M->'
191: 'M-?'
192: 'M-@'
193: 'M-A'
194: 'M-B'
195: 'M-C'
196: 'M-D'
197: 'M-E'
198: 'M-F'
199: 'M-G'
200: 'M-H'
201: 'M-I'
202: 'M-J'
203: 'M-K'
204: 'M-L'
205: 'M-M'
206: 'M-N'
207: 'M-O'
208: 'M-P'
209: 'M-Q'
210: 'M-R'
211: 'M-S'
212: 'M-T'
213: 'M-U'
214: 'M-V'
215: 'M-W'
216: 'M-X'
217: 'M-Y'
218: 'M-Z'
219: 'M-['
220: 'M-\'
221: 'M-]'
222: 'M-^'
223: 'M-_'
224: 'M-`'
225: 'M-a'
226: 'M-b'
227: 'M-c'
228: 'M-d'
229: 'M-e'
230: 'M-f'
231: 'M-g'
232: 'M-h'
233: 'M-i'
234: 'M-j'
235: 'M-k'
236: 'M-l'
237: 'M-m'
238: 'M-n'
239: 'M-o'
240: 'M-p'
241: 'M-q'
242: 'M-r'
243: 'M-s'
244: 'M-t'
245: 'M-u'
246: 'M-v'
247: 'M-w'
248: 'M-x'
249: 'M-y'
250: 'M-z'
251: 'M-{'
252: 'M-|'
253: 'M-}'
254: 'M-~'
255: 'M-^?'
$

Last edited by DGPickett; 09-06-2013 at 07:13 PM..
 

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