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  one of the values `unlimited', which
       removes the limit on the resource, or  `hard',  which  uses  the
       current value of the hard limit on the resource.

       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 value is 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 reason 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.
