BREAK(1)                   POSIX Programmer's Manual                  BREAK(1)



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

NNAAMMEE
       break -- exit from for, while, or until loop

SSYYNNOOPPSSIISS
       break [[_n]]

DDEESSCCRRIIPPTTIIOONN
       If _n is specified, the _b_r_e_a_k utility shall exit from the _nth enclosing
       ffoorr, wwhhiillee, or uunnttiill loop. If _n is not specified, _b_r_e_a_k 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 _b_r_e_a_k or _c_o_n_t_i_n_u_e command if the loop lexically
       encloses the command. A loop lexically encloses a _b_r_e_a_k or _c_o_n_t_i_n_u_e
       command if the command is:

        *  Executing in the same execution environment (see _S_e_c_t_i_o_n _2_._1_2,
           _S_h_e_l_l _E_x_e_c_u_t_i_o_n _E_n_v_i_r_o_n_m_e_n_t) as the compound-list of the loop's do-
           group (see _S_e_c_t_i_o_n _2_._1_0_._2, _S_h_e_l_l _G_r_a_m_m_a_r _R_u_l_e_s), 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 wwhhiillee
           or uunnttiill loop, in the compound-list following the wwhhiillee or uunnttiill
           reserved word), and

        *  Not in the body of a function whose function definition command
           (see _S_e_c_t_i_o_n _2_._9_._5, _F_u_n_c_t_i_o_n _D_e_f_i_n_i_t_i_o_n _C_o_m_m_a_n_d) 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 _b_r_e_a_k or _c_o_n_t_i_n_u_e command, it is unspecified whether
       that loop encloses the command.

OOPPTTIIOONNSS
       None.

OOPPEERRAANNDDSS
       See the DESCRIPTION.

SSTTDDIINN
       Not used.

IINNPPUUTT FFIILLEESS
       None.

EENNVVIIRROONNMMEENNTT VVAARRIIAABBLLEESS
       None.

AASSYYNNCCHHRROONNOOUUSS EEVVEENNTTSS
       Default.

SSTTDDOOUUTT
       Not used.

SSTTDDEERRRR
       The standard error shall be used only for diagnostic messages.

OOUUTTPPUUTT FFIILLEESS
       None.

EEXXTTEENNDDEEDD DDEESSCCRRIIPPTTIIOONN
       None.

EEXXIITT SSTTAATTUUSS
        0    Successful completion.

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

CCOONNSSEEQQUUEENNCCEESS OOFF EERRRROORRSS
       Default.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

EEXXAAMMPPLLEESS
       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 _b_r_e_a_k command is executed, and they are
       in the same execution environment, but neither loop is lexically
       enclosing the _b_r_e_a_k command. (There are no loops lexically enclosing
       the _c_o_n_t_i_n_u_e 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

RRAATTIIOONNAALLEE
       In early proposals, consideration was given to expanding the syntax of
       _b_r_e_a_k and _c_o_n_t_i_n_u_e 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.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _S_e_c_t_i_o_n _2_._1_4, _S_p_e_c_i_a_l _B_u_i_l_t_-_I_n _U_t_i_l_i_t_i_e_s

CCOOPPYYRRIIGGHHTT
       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 .



IEEE/The Open Group                  2017                             BREAK(1)
