User Commands                                            while(1)

NAME
     while, until - shell built-in functions to repetitively exe-
     cute  a  set of actions while/until conditions are evaluated
     TRUE

SYNOPSIS
  sh
     while [ conditions ]  ;  do  actions  ;  done

     until [ conditions ]  ;  do  actions  ;  done

  csh
     while (  conditions  )

      [ ... ]  # do actions

     end

  ksh
     while [ conditions ]  ;  do  actions  ;  done

     until [ conditions ]  ;  do  actions  ;  done

DESCRIPTION
  sh
     A while command repeatedly  executes  the  while  conditions
     and,  if  the  exit status of the last command in the condi-
     tions list is 0, executes the do actions; otherwise the loop
     terminates.  If  no commands in the do actions are executed,
     then the while command returns a 0 exit status; until may be
     used in place of while to negate the loop termination test.

  csh
     While conditions is TRUE (evaluates to nonzero), repeat com-
     mands  between the while and the matching end statement. The
     while and end must appear alone on their input lines. If the
     shell's  input is a terminal, it prompts for commands with a
     question-mark until the end command is entered and then per-
     forms the commands in the loop.

  ksh
     A while command repeatedly  executes  the  while  conditions
     and,  if  the  exit status of the last command in the condi-
     tions list is zero, executes the do actions;  otherwise  the
     loop  terminates.  If no commands in the do actions are exe-
     cuted, then the while command returns a 0 exit status; until
     may be used in place of while to negate the loop termination
     test.

  loop interrupts
     The built-in command continue may be used to  terminate  the
     execution of the current iteration of a while or until loop,

SunOS 5.8           Last change: 15 Apr 1994                    1

User Commands                                            while(1)

     and the built-in command break may be used to terminate exe-
     cution of a while or until command.

EXAMPLES
     Example 1: Using The while Command With sh and ksh

     In these examples, the user is repeated prompted for a  name
     of  a  file  to be located, until the user chooses to finish
     the execution by entering an empty line.

          filename=anything
          while [ $filename ]
          do
               echo "file?"
               read filename       # read from terminal
               find . -name $filename -print
          done
     The brackets surrounding $filename are necessary for evalua-
     tion. (See the test built-in command in the if(1) man page).
     Additionally, there must be a blank  space  separating  each
     bracket from any characters within.

     Example 2: Using The while Command With csh

     set filename = anything
          while ( "$filename" != "" )
               echo "file?"
               set filename = $<        # read from terminal
               find . -name $filename -print
          end

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcsu                     |
    |_____________________________|_____________________________|

SEE ALSO
     break(1), csh(1), if(1), ksh(1), sh(1), attributes(5)

NOTES
     Both the Bourne shell, sh, and the Korn shell, ksh, can  use
     the  semicolon  and  the  carriage return interchangeably in
     their syntax of the if, for, and while built-in commands.

SunOS 5.8           Last change: 15 Apr 1994                    2