控制字符知识普及

ASCII字符集的定义128个字符(0 to 127)，前32个值非打印控制字符(0-31以及127)，例如^G 7 表示bell(响铃)。

控制字符：

Char	八进制	十进制	十六进制	Control-Key	Control Action
NUL	0	0	0	^@	Null character
SOH	1	1	1	^A	Start of heading, = console interrupt
STX	2	2	2	^B	Start of text, maintenance mode on HP console
ETX	3	3	3	^C	End of text
EOT	4	4	4	^D	End of transmission, not the same as ETB
ENQ	5	5	5	^E	Enquiry, goes with ACK; old HP flow control
ACK	6	6	6	^F	Acknowledge, clears ENQ logon hand
BEL	7	7	7	^G	Bell, rings the bell...
BS	10	8	8	^H	Backspace, works on HP terminals/computers
HT	11	9	9	^I	Horizontal tab, move to next tab stop
LF	12	10	a	^J	Line Feed
VT	13	11	b	^K	Vertical tab
FF	14	12	c	^L	Form Feed, page eject
CR	15	13	d	^M	Carriage Return
SO	16	14	e	^N	Shift Out, alternate character set
SI	17	15	f	^O	Shift In, resume defaultn character set
DLE	20	16	10	^P	Data link escape
DC1	21	17	11	^Q	XON, with XOFF to pause listings; ":okay to send".
DC2	22	18	12	^R	Device control 2, block-mode flow control
DC3	23	19	13	^S	XOFF, with XON is TERM=18 flow control
DC4	24	20	14	^T	Device control 4
NAK	25	21	15	^U	Negative acknowledge
SYN	26	22	16	^V	Synchronous idle
ETB	27	23	17	^W	End transmission block, not the same as EOT
CAN	30	24	17	^X	Cancel line, MPE echoes !!!
EM	31	25	19	^Y	End of medium, Control-Y interrupt
SUB	32	26	1a	^Z	Substitute
ESC	33	27	1b	^[	Escape, next character is not echoed
FS	34	28	1c	^\	File separator
GS	35	29	1d	^]	Group separator
RS	36	30	1e	^^	Record separator, block-mode terminator
US	37	31	1f	^_	Unit separator

打印字符

Char	Octal	Dec	Hex	Description
SP	40	32	20	Space
!	41	33	21	Exclamation mark
"	42	34	22	Quotation mark (" in HTML)
#	43	35	23	Cross hatch (number sign)
$	44	36	24	Dollar sign
%	45	37	25	Percent sign
&	46	38	26	Ampersand
`	47	39	27	Closing single quote (apostrophe)
(	50	40	28	Opening parentheses
)	51	41	29	Closing parentheses
*	52	42	2a	Asterisk (star, multiply)
+	53	43	2b	Plus
,	54	44	2c	Comma
-	55	45	2d	Hyphen, dash, minus
.	56	46	2e	Period
/	57	47	2f	Slant (forward slash, divide)
0	60	48	30	Zero
1	61	49	31	One
2	62	50	32	Two
3	63	51	33	Three
4	64	52	34	Four
5	65	53	35	Five
6	66	54	36	Six
7	67	55	37	Seven
8	70	56	38	Eight
9	71	57	39	Nine
:	72	58	3a	Colon
;	73	59	3b	Semicolon
<	74	60	3c	Less than sign (< in HTML)
=	75	61	3d	Equals sign
>	76	62	3e	Greater than sign (> in HTML)
?	77	63	3f	Question mark
@	100	64	40	At-sign
A	101	65	41	Uppercase A
B	102	66	42	Uppercase B
C	103	67	43	Uppercase C
D	104	68	44	Uppercase D
E	105	69	45	Uppercase E
F	106	70	46	Uppercase F
G	107	71	47	Uppercase G
H	110	72	48	Uppercase H
I	111	73	49	Uppercase I
J	112	74	4a	Uppercase J
K	113	75	4b	Uppercase K
L	114	76	4c	Uppercase L
M	115	77	4d	Uppercase M
N	116	78	4e	Uppercase N
O	117	79	4f	Uppercase O
P	120	80	50	Uppercase P
Q	121	81	51	Uppercase Q
R	122	82	52	Uppercase R
S	123	83	53	Uppercase S
T	124	84	54	Uppercase T
U	125	85	55	Uppercase U
V	126	86	56	Uppercase V
W	127	87	57	Uppercase W
X	130	88	58	Uppercase X
Y	131	89	59	Uppercase Y
Z	132	90	5a	Uppercase Z
[	133	91	5b	Opening square bracket
\	134	92	5c	Reverse slant (Backslash)
]	135	93	5d	Closing square bracket
^	136	94	5e	Caret (Circumflex)
_	137	95	5f	Underscore
`	140	96	60	Opening single quote
a	141	97	61	Lowercase a
b	142	98	62	Lowercase b
c	143	99	63	Lowercase c
d	144	100	64	Lowercase d
e	145	101	65	Lowercase e
f	146	102	66	Lowercase f
g	147	103	67	Lowercase g
h	150	104	68	Lowercase h
i	151	105	69	Lowercase i
j	152	106	6a	Lowercase j
k	153	107	6b	Lowercase k
l	154	108	6c	Lowercase l
m	155	109	6d	Lowercase m
n	156	110	6e	Lowercase n
o	157	111	6f	Lowercase o
p	160	112	70	Lowercase p
q	161	113	71	Lowercase q
r	162	114	72	Lowercase r
s	163	115	73	Lowercase s
t	164	116	74	Lowercase t
u	165	117	75	Lowercase u
v	166	118	76	Lowercase v
w	167	119	77	Lowercase w
x	170	120	78	Lowercase x
y	171	121	79	Lowercase y
z	172	122	7a	Lowercase z
{	173	123	7b	Opening curly brace
|	174	124	7c	Vertical line
}	175	125	7d	Cloing curly brace
~	176	126	7e	Tilde (approximate)
DEL	177	127	7f	Delete (rubout), cross-hatch box

shell中处理控制字符：

有时候文本中会留有控制符，比如test1：

需要用cat -v  或者cat -A 才可以看到控制字符^A

21.703073010384102^A24.714308723165203^A27.38294439629967^A32.307091875806^A76429^A209438

现在需要把^A转换为空格。^A是1(或01、001)，空格是40(或040)。重定向到test2。

tr -s "[\001]" "[\040*]" test2