ulimit [ [ -SHacdfilmnpqstvx | -N resource [ limit ] ... ]
       Set or display resource limits of the shell  and  the  processes
       started by the shell.  The value of limit can be a number in the
       unit specified below or the value `unlimited'.  By default, only
       soft  limits  are  manipulated. If the -H flag is given use hard
       limits instead of soft limits.  If the -S flag is given together
       with  the  -H flag set both hard and soft limits.  If no options
       are used, the file size limit (-f)  is  assumed.   If  limit  is
       omitted  the  current  value  of  the  specified  resources  are
       printed.  When more than one resource  values  are  printed  the
       limit name and unit is printed before each value.

       When looping over multiple resources, the shell will abort imme-
       diately if it detects a badly formed argument.  However,  if  it
       fails  to set a limit for some other reson it will continue try-
       ing to set the remaining limits.

       -a     Lists all of the current resource limits.
       -c     512-byte blocks on the size of core dumps.
       -d     K-bytes on the size of the data segment.
       -f     512-byte blocks on the size of files written.
       -i     The number of pending signals.
       -l     K-bytes on the size of locked-in memory.
       -m     K-bytes on the size of physical memory.
       -n     open file descriptors.
       -q     Bytes in POSIX message queues.
       -s     K-bytes on the size of the stack.
       -t     CPU seconds to be used.
       -u     processes available to the user.
       -v     K-bytes on the size of virtual memory.  On  some  systems
              this refers to the limit called `address space'.
       -x     The number of locks on files.

       A  resource  may  also  be  specified by integer in the form `-N
       resource', where resource corresponds to the integer defined for
       the  resource  by the operating system.  This may be used to set
       the limits for resources known to the shell which do not  corre-
       spond to option letters.  Such limits will be shown by number in
       the output of `ulimit -a'.

       The number may alternatively be out of the range of limits  com-
       piled  into  the shell.  The shell will try to read or write the
       limit anyway, and will report an error if this fails.
