PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       break — exit from for, while, or until loop

SYNOPSIS

       break [n]

DESCRIPTION

       If  n  is  specified,  the  break utility shall exit from the nth enclosing for, while, or
       until loop. If n is not specified, break  shall  behave  as  if  n  was  specified  as  1.
       Execution shall continue with the command immediately following the exited loop. The value
       of n is a positive decimal integer. If n is greater than the number  of  enclosing  loops,
       the  outermost enclosing loop shall be exited. If there is no enclosing loop, the behavior
       is unspecified.

       A loop shall enclose a break or continue  command  if  the  loop  lexically  encloses  the
       command. A loop lexically encloses a break or continue command if the command is:

        *  Executing  in  the  same  execution  environment  (see  Section  2.12, Shell Execution
           Environment) as the compound-list of the loop's do-group (see  Section  2.10.2,  Shell
           Grammar Rules), and

        *  Contained  in a compound-list associated with the loop (either in the compound-list of
           the loop's do-group or, if the loop is a while or until  loop,  in  the  compound-list
           following the while or until reserved word), and

        *  Not  in  the  body of a function whose function definition command (see Section 2.9.5,
           Function Definition Command) is contained in a compound-list associated with the loop.

       If n is greater than the number of lexically enclosing loops and there is a  non-lexically
       enclosing  loop  in  progress  in  the same execution environment as the break or continue
       command, it is unspecified whether that loop encloses the command.

OPTIONS

       None.

OPERANDS

       See the DESCRIPTION.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       None.

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       Not used.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

        0    Successful completion.

       >0    The n value was not an unsigned decimal integer greater than or equal to 1.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       for i in *
       do
           if test -d "$i"
           then break
           fi
       done

       The results of running the following example are  unspecified:  there  are  two  loops  in
       progress  when  the  break  command  is  executed,  and  they  are  in  the same execution
       environment, but neither loop is lexically enclosing the  break  command.  (There  are  no
       loops lexically enclosing the continue commands, either.)

       foo() {
           for j in 1 2; do
               echo 'break 2' >/tmp/do_break
               echo "  sourcing /tmp/do_break ($j)..."
               # the behavior of the break from running the following command
               # results in unspecified behavior:
               . /tmp/do_break

               do_continue() { continue 2; }
               echo "  running do_continue ($j)..."
               # the behavior of the continue in the following function call
               # results in unspecified behavior (if execution reaches this
               # point):
               do_continue

               trap 'continue 2' USR1
               echo "  sending SIGUSR1 to self ($j)..."
               # the behavior of the continue in the trap invoked from the
               # following signal results in unspecified behavior (if
               # execution reaches this point):
               kill -s USR1 $$
               sleep 1
           done
       }
       for i in 1 2; do
           echo "running foo ($i)..."
           foo
       done

RATIONALE

       In  early proposals, consideration was given to expanding the syntax of break and continue
       to refer to a label associated with the appropriate loop as a  preferable  alternative  to
       the  n method. However, this volume of POSIX.1‐2017 does reserve the name space of command
       names ending with a <colon>.  It is anticipated that a future  implementation  could  take
       advantage of this and provide something like:

           outofloop: for i in a b c d e
           do
               for j in 0 1 2 3 4 5 6 7 8 9
               do
                   if test -r "${i}${j}"
                   then break outofloop
                   fi
               done
           done

       and that this might be standardized after implementation experience is achieved.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.14, Special Built-In Utilities

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .