1ECHO(1P) POSIX Programmer's Manual ECHO(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 echo - write arguments to standard output
13
15 echo [string ...]
16
18 The echo utility writes its arguments to standard output, followed by a
19 <newline>. If there are no arguments, only the <newline> is written.
20
22 The echo utility shall not recognize the "--" argument in the manner
23 specified by Guideline 10 of the Base Definitions volume of
24 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines; "--"
25 shall be recognized as a string operand.
26 Implementations shall not support any options.
28
30 The following operands shall be supported:
31 string A string to be written to standard output. If the first operand
33 is -n, or if any of the operands contain a backslash ( '\' )
34 character, the results are implementation-defined.
35 On XSI-conformant systems, if the first operand is -n, it shall be
37 treated as a string, not an option. The following character sequences
38 shall be recognized on XSI-conformant systems within any of the argu‐
39 ments:
40 \a
42 Write an <alert>.
43 \b
45 Write a <backspace>.
46 \c
48 Suppress the <newline> that otherwise follows the final argument
49 in the output. All characters following the '\c' in the argu‐
50 ments shall be ignored.
51 \f
53 Write a <form-feed>.
54 \n
56 Write a <newline>.
57 \r
59 Write a <carriage-return>.
60 \t
62 Write a <tab>.
63 \v
65 Write a <vertical-tab>.
66 \\
68 Write a backslash character.
69 \0num
71 Write an 8-bit value that is the zero, one, two, or three-digit
72 octal number num.
73
77 Not used.
78
80 None.
81
83 The following environment variables shall affect the execution of echo:
84 LANG Provide a default value for the internationalization variables
86 that are unset or null. (See the Base Definitions volume of
87 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
88 ables for the precedence of internationalization variables used
89 to determine the values of locale categories.)
90 LC_ALL If set to a non-empty string value, override the values of all
92 the other internationalization variables.
93 LC_CTYPE
95 Determine the locale for the interpretation of sequences of
96 bytes of text data as characters (for example, single-byte as
97 opposed to multi-byte characters in arguments).
98 LC_MESSAGES
100 Determine the locale that should be used to affect the format
101 and contents of diagnostic messages written to standard error.
102 NLSPATH
104 Determine the location of message catalogs for the processing of
105 LC_MESSAGES .
106
109 Default.
110
112 The echo utility arguments shall be separated by single <space>s and a
113 <newline> shall follow the last argument. Output transformations shall
114 occur based on the escape sequences in the input. See the OPERANDS sec‐
115 tion.
116
118 The standard error shall be used only for diagnostic messages.
119
121 None.
122
124 None.
125
127 The following exit values shall be returned:
128 0 Successful completion.
130 >0 An error occurred.
132
135 Default.
136 The following sections are informative.
138
140 It is not possible to use echo portably across all POSIX systems unless
141 both -n (as the first argument) and escape sequences are omitted.
142 The printf utility can be used portably to emulate any of the tradi‐
144 tional behaviors of the echo utility as follows (assuming that IFS has
145 its standard value or is unset):
146 * The historic System V echo and the requirements on XSI implementa‐
148 tions in this volume of IEEE Std 1003.1-2001 are equivalent to:
149 printf "%b\n" "$*"
152 * The BSD echo is equivalent to:
154 if [ "X$1" = "X-n" ]
157 then
158 shift
159 printf "%s" "$*"
160 else
161 printf "%s\n" "$*"
162 fi
163 New applications are encouraged to use printf instead of echo.
165
167 None.
168
170 The echo utility has not been made obsolescent because of its extremely
171 widespread use in historical applications. Conforming applications
172 that wish to do prompting without <newline>s or that could possibly be
173 expecting to echo a -n, should use the printf utility derived from the
174 Ninth Edition system.
175 As specified, echo writes its arguments in the simplest of ways. The
177 two different historical versions of echo vary in fatally incompatible
178 ways.
179 The BSD echo checks the first argument for the string -n which causes
181 it to suppress the <newline> that would otherwise follow the final
182 argument in the output.
183 The System V echo does not support any options, but allows escape
185 sequences within its operands, as described for XSI implementations in
186 the OPERANDS section.
187 The echo utility does not support Utility Syntax Guideline 10 because
189 historical applications depend on echo to echo all of its arguments,
190 except for the -n option in the BSD version.
191
193 None.
194
196 printf
197
199 Portions of this text are reprinted and reproduced in electronic form
200 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
201 -- Portable Operating System Interface (POSIX), The Open Group Base
202 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
203 Electrical and Electronics Engineers, Inc and The Open Group. In the
204 event of any discrepancy between this version and the original IEEE and
205 The Open Group Standard, the original IEEE and The Open Group Standard
206 is the referee document. The original Standard can be obtained online
207 at http://www.opengroup.org/unix/online.html .
208IEEE/The Open Group 2003 ECHO(1P)