1BREAK(1P) POSIX Programmer's Manual BREAK(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 break — exit from for, while, or until loop
13
15 break [n]
16
18 If n is specified, the break utility shall exit from the nth enclosing
19 for, while, or until loop. If n is not specified, break shall behave as
20 if n was specified as 1. Execution shall continue with the command
21 immediately following the exited loop. The value of n is a positive
22 decimal integer. If n is greater than the number of enclosing loops,
23 the outermost enclosing loop shall be exited. If there is no enclosing
24 loop, the behavior is unspecified.
25 A loop shall enclose a break or continue command if the loop lexically
27 encloses the command. A loop lexically encloses a break or continue
28 command if the command is:
29 * Executing in the same execution environment (see Section 2.12,
31 Shell Execution Environment) as the compound-list of the loop's do-
32 group (see Section 2.10.2, Shell Grammar Rules), and
33 * Contained in a compound-list associated with the loop (either in
35 the compound-list of the loop's do-group or, if the loop is a while
36 or until loop, in the compound-list following the while or until
37 reserved word), and
38 * Not in the body of a function whose function definition command
40 (see Section 2.9.5, Function Definition Command) is contained in a
41 compound-list associated with the loop.
42 If n is greater than the number of lexically enclosing loops and there
44 is a non-lexically enclosing loop in progress in the same execution
45 environment as the break or continue command, it is unspecified whether
46 that loop encloses the command.
47
49 None.
50
52 See the DESCRIPTION.
53
55 Not used.
56
58 None.
59
61 None.
62
64 Default.
65
67 Not used.
68
70 The standard error shall be used only for diagnostic messages.
71
73 None.
74
76 None.
77
79 0 Successful completion.
80 >0 The n value was not an unsigned decimal integer greater than or
82 equal to 1.
83
85 Default.
86 The following sections are informative.
88
90 None.
91
93 for i in *
94 do
95 if test -d "$i"
96 then break
97 fi
98 done
99 The results of running the following example are unspecified: there are
101 two loops in progress when the break command is executed, and they are
102 in the same execution environment, but neither loop is lexically
103 enclosing the break command. (There are no loops lexically enclosing
104 the continue commands, either.)
105 foo() {
107 for j in 1 2; do
108 echo 'break 2' >/tmp/do_break
109 echo " sourcing /tmp/do_break ($j)..."
110 # the behavior of the break from running the following command
111 # results in unspecified behavior:
112 . /tmp/do_break
113 do_continue() { continue 2; }
115 echo " running do_continue ($j)..."
116 # the behavior of the continue in the following function call
117 # results in unspecified behavior (if execution reaches this
118 # point):
119 do_continue
120 trap 'continue 2' USR1
122 echo " sending SIGUSR1 to self ($j)..."
123 # the behavior of the continue in the trap invoked from the
124 # following signal results in unspecified behavior (if
125 # execution reaches this point):
126 kill -s USR1 $$
127 sleep 1
128 done
129 }
130 for i in 1 2; do
131 echo "running foo ($i)..."
132 foo
133 done
134
136 In early proposals, consideration was given to expanding the syntax of
137 break and continue to refer to a label associated with the appropriate
138 loop as a preferable alternative to the n method. However, this volume
139 of POSIX.1‐2017 does reserve the name space of command names ending
140 with a <colon>. It is anticipated that a future implementation could
141 take advantage of this and provide something like:
142 outofloop: for i in a b c d e
145 do
146 for j in 0 1 2 3 4 5 6 7 8 9
147 do
148 if test -r "${i}${j}"
149 then break outofloop
150 fi
151 done
152 done
153 and that this might be standardized after implementation experience is
155 achieved.
156
158 None.
159
161 Section 2.14, Special Built-In Utilities
162
164 Portions of this text are reprinted and reproduced in electronic form
165 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
166 table Operating System Interface (POSIX), The Open Group Base Specifi‐
167 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
168 Electrical and Electronics Engineers, Inc and The Open Group. In the
169 event of any discrepancy between this version and the original IEEE and
170 The Open Group Standard, the original IEEE and The Open Group Standard
171 is the referee document. The original Standard can be obtained online
172 at http://www.opengroup.org/unix/online.html .
173 Any typographical or formatting errors that appear in this page are
175 most likely to have been introduced during the conversion of the source
176 files to man page format. To report such errors, see https://www.ker‐
177 nel.org/doc/man-pages/reporting_bugs.html .
178IEEE/The Open Group 2017 BREAK(1P)