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                        <'               [duration]\n'>
                        <'                 -d device       # device string (eg, '>
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                        <
'                 -i iotype       # match type (eg, \'*R*\' for all reads)\n'
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                        <'                 -Q              # use queue insert as start time\n'>
                        <'                 -s              # include start time of I/O (s)\n'>
                        <'                 -t              # include completion time of I/O (s)\n'>
                        <'                 -h              # this usage message\n'>
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                        <'       iosnoop 1                 # trace 1 sec (buffered)\n'>
                        <'       iosnoop -Q                # include queueing time in LATms\n'>
                        <'       iosnoop -ts               # include start and end timestamps\n'>
                        <'       iosnoop -i \'*R*\'          # trace reads\n'>
                        <
'       iosnoop -p 91             # show I/O issued when PID 91 is on-CPU\n'
                        >
                        <
'       iosnoop -Qp 91            # show I/O queued by PID 91, queue time\n'
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                                left: ($ Id.Lit_ArithVarLike major)
                                right: {<Id.Lit_Digits 20>}
                              )
                            right: ($ Id.Lit_ArithVarLike minor)
                          )
                      )
                    }
                  spids: [693]
                )
              ]
              redirects: []
            )
          ]
          spids: [662 672]
        )
      ]
      else_action: []
      redirects: []
    )
    (command.AndOr
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      children: [
        (command.DParen
          child: 
            (arith_expr.Binary
              op_id: Id.Arith_DAmp
              left: ($ Id.Lit_ArithVarLike opt_pid)
              right: ($ Id.Lit_ArithVarLike opt_name)
            )
          redirects: []
        )
        (C {<die>} {(DQ <'ERROR: use either -p or -n.'>)})
      ]
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DParen child:($ Id.Lit_ArithVarLike opt_pid) redirects:[])
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'ftext='> name:ftext)
              op: assign_op.Equal
              rhs: {(DQ <' issued by PID '> ($ Id.VSub_DollarName pid))}
              spids: [745]
            )
          ]
          redirects: []
        )
      ]
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DParen child:($ Id.Lit_ArithVarLike opt_name) redirects:[])
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'ftext='> name:ftext)
              op: assign_op.Equal
              rhs: 
                {
                  (DQ <' issued by process name '> 
                    (word_part.EscapedLiteral
                      token: <Id.Lit_EscapedChar '\\"'>
                      ch: '"'
                    ) ($ Id.VSub_DollarName name) (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'> ch:'"')
                  )
                }
              spids: [760]
            )
          ]
          redirects: []
        )
      ]
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: (command.DParen child:($ Id.Lit_ArithVarLike opt_duration) redirects:[])
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (C {<echo>} 
              {
                (DQ <'Tracing block I/O'> ($ Id.VSub_DollarName ftext) <' for '> 
                  ($ Id.VSub_DollarName duration) <' seconds (buffered)...'>
                )
              }
            )
          ]
          spids: [768 778]
        )
      ]
      else_action: [
        (C {<echo>} {(DQ <'Tracing block I/O'> ($ Id.VSub_DollarName ftext) <'. Ctrl-C to end.'>)})
      ]
      redirects: []
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: (command.DParen child:($ Id.Lit_ArithVarLike opt_queue) redirects:[])
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (command.ShAssignment
              pairs: [
                (assign_pair
                  lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'b_start='> name:b_start)
                  op: assign_op.Equal
                  rhs: {<block_rq_insert>}
                  spids: [817]
                )
              ]
              redirects: []
            )
          ]
          spids: [804 814]
        )
      ]
      else_action: [
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'b_start='> name:b_start)
              op: assign_op.Equal
              rhs: {<block_rq_issue>}
              spids: [823]
            )
          ]
          redirects: []
        )
      ]
      redirects: []
    )
    (command.AndOr
      ops: [Id.Op_DAmp Id.Op_DPipe]
      children: [
        (command.DParen child:($ Id.Lit_ArithVarLike opt_duration) redirects:[])
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'use='> name:use)
              op: assign_op.Equal
              rhs: {<mawk>}
              spids: [841]
            )
          ]
          redirects: []
        )
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'use='> name:use)
              op: assign_op.Equal
              rhs: {<gawk>}
              spids: [846]
            )
          ]
          redirects: []
        )
      ]
    )
    (command.AndOr
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      children: [
        (command.DBracket
          expr: (bool_expr.Unary op_id:Id.BoolUnary_x child:{<'/usr/bin/'> ($ Id.VSub_DollarName use)})
          redirects: []
        )
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'awk='> name:awk)
              op: assign_op.Equal
              rhs: {($ Id.VSub_DollarName use)}
              spids: [863]
            )
          ]
          redirects: []
        )
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'awk='> name:awk)
              op: assign_op.Equal
              rhs: {<awk>}
              spids: [868]
            )
          ]
          redirects: []
        )
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    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'wroteflock='> name:wroteflock)
          op: assign_op.Equal
          rhs: {<1>}
          spids: [871]
        )
      ]
      redirects: []
    )
    (command.AndOr
      ops: [Id.Op_DPipe]
      children: [
        (C {<cd>} {($ Id.VSub_DollarName tracing)})
        (C {<die>} 
          {
            (DQ <'ERROR: accessing tracing. Root user? Kernel has FTRACE?\n'> 
              <'    debugfs mounted? (mount -t debugfs debugfs /sys/kernel/debug)'>
            )
          }
        )
      ]
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DBracket
          expr: (bool_expr.Unary op_id:Id.BoolUnary_e child:{($ Id.VSub_DollarName flock)})
          redirects: []
        )
        (C {<die>} 
          {
            (DQ <'ERROR: ftrace may be in use by PID '> 
              (command_sub
                left_token: <Id.Left_DollarParen '$('>
                child: (C {<cat>} {($ Id.VSub_DollarName flock)})
                right: <Id.Eof_RParen _>
              ) <' '> ($ Id.VSub_DollarName flock)
            )
          }
        )
      ]
    )
    (command.AndOr
      ops: [Id.Op_DPipe]
      children: [
        (command.Simple
          words: [{<echo>} {($ Id.VSub_Dollar '$')}]
          redirects: [
            (redir
              op: <Id.Redir_Great '>'>
              loc: (redir_loc.Fd fd:1)
              arg: {($ Id.VSub_DollarName flock)}
            )
          ]
          more_env: []
          do_fork: T
        )
        (C {<die>} {(DQ <'ERROR: unable to write '> ($ Id.VSub_DollarName flock) <.>)})
      ]
    )
    (command.Simple
      words: [{<echo>} {<nop>}]
      redirects: [(redir op:<Id.Redir_Great '>'> loc:(redir_loc.Fd fd:1) arg:{<current_tracer>})]
      more_env: []
      do_fork: T
    )
    (C {<warn>} {(DQ <'echo '> ($ Id.VSub_DollarName bufsize_kb) <' > buffer_size_kb'>)})
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter='> name:filter)
          op: assign_op.Equal
          rhs: (rhs_word.Empty)
          spids: [956]
        )
      ]
      redirects: []
    )
    (command.If
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        (if_arm
          cond: 
            (condition.Shell
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                (command.Sentence
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                  terminator: <Id.Op_Semi _>
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              ]
            )
          action: [
            (command.ShAssignment
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                (assign_pair
                  lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter='> name:filter)
                  op: assign_op.Equal
                  rhs: 
                    {
                      (DQ <'rwbs ~ '> 
                        (word_part.EscapedLiteral
                          token: <Id.Lit_EscapedChar '\\"'>
                          ch: '"'
                        ) ($ Id.VSub_DollarName iotype) (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'> ch:'"')
                      )
                    }
                  spids: [971]
                )
              ]
              redirects: []
            )
          ]
          spids: [958 968]
        )
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      else_action: []
      redirects: []
    )
    (command.If
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        (if_arm
          cond: 
            (condition.Shell
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                  terminator: <Id.Op_Semi _>
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            )
          action: [
            (command.AndOr
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              children: [
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                      left: {(DQ ($ Id.VSub_DollarName filter))}
                      right: {(DQ )}
                    )
                  redirects: []
                )
                (command.ShAssignment
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                    (assign_pair
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                      op: assign_op.Equal
                      rhs: {(DQ ($ Id.VSub_DollarName filter) <' && '>)}
                      spids: [1009]
                    )
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                  redirects: []
                )
              ]
            )
            (command.ShAssignment
              pairs: [
                (assign_pair
                  lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter='> name:filter)
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                  rhs: {(DQ (${ Id.VSub_Name filter) <'dev == '> ($ Id.VSub_DollarName dev))}
                  spids: [1016]
                )
              ]
              redirects: []
            )
          ]
          spids: [981 991]
        )
      ]
      else_action: []
      redirects: []
    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter_i='> name:filter_i)
          op: assign_op.Equal
          rhs: {($ Id.VSub_DollarName filter)}
          spids: [1027]
        )
      ]
      redirects: []
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: (command.DParen child:($ Id.Lit_ArithVarLike opt_pid) redirects:[])
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (command.AndOr
              ops: [Id.Op_DAmp]
              children: [
                (command.DBracket
                  expr: 
                    (bool_expr.Binary
                      op_id: Id.BoolBinary_GlobNEqual
                      left: {(DQ ($ Id.VSub_DollarName filter_i))}
                      right: {(DQ )}
                    )
                  redirects: []
                )
                (command.ShAssignment
                  pairs: [
                    (assign_pair
                      lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter_i='> name:filter_i)
                      op: assign_op.Equal
                      rhs: {(DQ ($ Id.VSub_DollarName filter_i) <' && '>)}
                      spids: [1058]
                    )
                  ]
                  redirects: []
                )
              ]
            )
            (command.ShAssignment
              pairs: [
                (assign_pair
                  lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter_i='> name:filter_i)
                  op: assign_op.Equal
                  rhs: {(DQ (${ Id.VSub_Name filter_i) <'common_pid == '> ($ Id.VSub_DollarName pid))}
                  spids: [1065]
                )
              ]
              redirects: []
            )
            (command.AndOr
              ops: [Id.Op_DAmp]
              children: [
                (command.DBracket
                  expr: 
                    (bool_expr.Binary
                      op_id: Id.BoolBinary_GlobDEqual
                      left: {(DQ ($ Id.VSub_DollarName filter))}
                      right: {(DQ )}
                    )
                  redirects: []
                )
                (command.ShAssignment
                  pairs: [
                    (assign_pair
                      lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'filter='> name:filter)
                      op: assign_op.Equal
                      rhs: {<0>}
                      spids: [1090]
                    )
                  ]
                  redirects: []
                )
              ]
            )
          ]
          spids: [1030 1040]
        )
      ]
      else_action: []
      redirects: []
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: 
                    (command.DParen
                      child: 
                        (arith_expr.Binary
                          op_id: Id.Arith_DPipe
                          left: 
                            (arith_expr.Binary
                              op_id: Id.Arith_DPipe
                              left: ($ Id.Lit_ArithVarLike opt_iotype)
                              right: ($ Id.Lit_ArithVarLike opt_device)
                            )
                          right: ($ Id.Lit_ArithVarLike opt_pid)
                        )
                      redirects: []
                    )
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (command.If
              arms: [
                (if_arm
                  cond: 
                    (condition.Shell
                      commands: [
                        (command.AndOr
                          ops: [Id.Op_DPipe]
                          children: [
                            (command.Pipeline
                              children: [
                                (command.Simple
                                  words: [{<echo>} {(DQ ($ Id.VSub_DollarName filter_i))}]
                                  redirects: [
                                    (redir
                                      op: <Id.Redir_Great '>'>
                                      loc: (redir_loc.Fd fd:1)
                                      arg: 
                                        {<'events/block/'> ($ Id.VSub_DollarName b_start) <'/filter'>}
                                    )
                                  ]
                                  more_env: []
                                  do_fork: T
                                )
                              ]
                              negated: T
                              stderr_indices: []
                            )
                            (command.Pipeline
                              children: [
                                (command.Simple
                                  words: [{<echo>} {(DQ ($ Id.VSub_DollarName filter))}]
                                  redirects: [
                                    (redir
                                      op: <Id.Redir_Great '>'>
                                      loc: (redir_loc.Fd fd:1)
                                      arg: {<'events/block/block_rq_complete/filter'>}
                                    )
                                  ]
                                  more_env: []
                                  do_fork: T
                                )
                              ]
                              negated: T
                              stderr_indices: []
                            )
                          ]
                        )
                      ]
                    )
                  action: [(C {<edie>} {(DQ <'ERROR: setting -d or -t filter. Exiting.'>)})]
                  spids: [1116 1149]
                )
              ]
              else_action: []
              redirects: []
            )
          ]
          spids: [1095 1113]
        )
      ]
      else_action: []
      redirects: []
    )
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: 
                    (command.AndOr
                      ops: [Id.Op_DPipe]
                      children: [
                        (command.Pipeline
                          children: [
                            (command.Simple
                              words: [{<echo>} {<1>}]
                              redirects: [
                                (redir
                                  op: <Id.Redir_Great '>'>
                                  loc: (redir_loc.Fd fd:1)
                                  arg: {<'events/block/'> ($ Id.VSub_DollarName b_start) <'/enable'>}
                                )
                              ]
                              more_env: []
                              do_fork: T
                            )
                          ]
                          negated: T
                          stderr_indices: []
                        )
                        (command.Pipeline
                          children: [
                            (command.Simple
                              words: [{<echo>} {<1>}]
                              redirects: [
                                (redir
                                  op: <Id.Redir_Great '>'>
                                  loc: (redir_loc.Fd fd:1)
                                  arg: {<'events/block/block_rq_complete/enable'>}
                                )
                              ]
                              more_env: []
                              do_fork: T
                            )
                          ]
                          negated: T
                          stderr_indices: []
                        )
                      ]
                    )
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [(C {<edie>} {(DQ <'ERROR: enabling block I/O tracepoints. Exiting.'>)})]
          spids: [1163 1192]
        )
      ]
      else_action: []
      redirects: []
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DParen child:($ Id.Lit_ArithVarLike opt_start) redirects:[])
        (C {<printf>} {(DQ <'%-15s '>)} {(DQ <STARTs>)})
      ]
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DParen child:($ Id.Lit_ArithVarLike opt_end) redirects:[])
        (C {<printf>} {(DQ <'%-15s '>)} {(DQ <ENDs>)})
      ]
    )
    (C {<printf>} {(DQ <'%-12.12s %-6s %-4s %-8s %-12s %-6s %8s'> <Id.Lit_BadBackslash '\\'> <n>)} 
      {(DQ <COMM>)} {(DQ <PID>)} {(DQ <TYPE>)} {(DQ <DEV>)} {(DQ <BLOCK>)} {(DQ <BYTES>)} {(DQ <LATms>)}
    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name left:<Id.Lit_VarLike 'offset='> name:offset)
          op: assign_op.Equal
          rhs: 
            {
              (command_sub
                left_token: <Id.Left_DollarParen '$('>
                child: 
                  (C {($ Id.VSub_DollarName awk)} 
                    {
                      (SQ <'BEGIN { o = 0; }\n'> 
                        <'\t$1 == "#" && $2 ~ /TASK/ && NF == 6 { o = 1; }\n'> <'\t$2 ~ /TASK/ { print o; exit }'>
                      )
                    } {<trace>}
                  )
                right: <Id.Eof_RParen _>
              )
            }
          spids: [1301]
        )
      ]
      redirects: []
    )
    (C {<warn>} {(DQ <'echo > trace'>)})
    (command.Pipeline
      children: [
        (command.Subshell
          child: 
            (command.If
              arms: [
                (if_arm
                  cond: 
                    (condition.Shell
                      commands: [
                        (command.Sentence
                          child: 
                            (command.DParen
                              child: ($ Id.Lit_ArithVarLike opt_duration)
                              redirects: []
                            )
                          terminator: <Id.Op_Semi _>
                        )
                      ]
                    )
                  action: [(C {<sleep>} {($ Id.VSub_DollarName duration)}) (C {<cat>} {<trace>})]
                  spids: [1326 1336]
                )
              ]
              else_action: [(C {<cat>} {<trace_pipe>})]
              redirects: []
            )
          redirects: []
        )
        (C {($ Id.VSub_DollarName awk)} {<-v>} {<Id.Lit_VarLike 'o='> ($ Id.VSub_DollarName offset)} 
          {<-v>} {<Id.Lit_VarLike 'opt_name='> ($ Id.VSub_DollarName opt_name)} {<-v>} 
          {<Id.Lit_VarLike 'name='> ($ Id.VSub_DollarName name)} {<-v>} {<Id.Lit_VarLike 'opt_duration='> ($ Id.VSub_DollarName opt_duration)} {<-v>} 
          {<Id.Lit_VarLike 'opt_start='> ($ Id.VSub_DollarName opt_start)} {<-v>} {<Id.Lit_VarLike 'opt_end='> ($ Id.VSub_DollarName opt_end)} {<-v>} 
          {<Id.Lit_VarLike 'b_start='> ($ Id.VSub_DollarName b_start)} 
          {
            (SQ <'\n'> <'\t# common fields\n'> <'\t$1 != "#" {\n'> 
              <'\t\t# task name can contain dashes\n'> <'\t\tcomm = pid = $1\n'> <'\t\tsub(/-[0-9][0-9]*/, "", comm)\n'> <'\t\tsub(/.*-/, "", pid)\n'> 
              <'\t\ttime = $(3+o); sub(":", "", time)\n'> <'\t\tdev = $(5+o)\n'> <'\t}\n'> <'\n'> <'\t# block I/O request\n'> <'\t$1 != "#" && $0 ~ b_start {\n'> 
              <'\t\tif (opt_name && match(comm, name) == 0)\n'> <'\t\t\tnext\n'> <'\t\t#\n'> <'\t\t# example: (fields1..4+o) 202,1 W 0 () 12862264 + 8 [tar]\n'> 
              <'\t\t# The cmd field "()" might contain multiple words (hex),\n'> <'\t\t# hence stepping from the right (NF-3).\n'> <'\t\t#\n'> <'\t\tloc = $(NF-3)\n'> 
              <'\t\tstarts[dev, loc] = time\n'> <'\t\tcomms[dev, loc] = comm\n'> <'\t\tpids[dev, loc] = pid\n'> <'\t\tnext\n'> <'\t}\n'> <'\n'> 
              <'\t# block I/O completion\n'> <'\t$1 != "#" && $0 ~ /rq_complete/ {\n'> <'\t\t#\n'> 
              <'\t\t# example: (fields1..4+o) 202,1 W () 12862256 + 8 [0]\n'> <'\t\t#\n'> <'\t\tdir = $(6+o)\n'> <'\t\tloc = $(NF-3)\n'> <'\t\tnsec = $(NF-1)\n'> <'\n'> 
              <'\t\tif (starts[dev, loc] > 0) {\n'> <'\t\t\tlatency = sprintf("%.2f",\n'> <'\t\t\t    1000 * (time - starts[dev, loc]))\n'> 
              <'\t\t\tcomm = comms[dev, loc]\n'> <'\t\t\tpid = pids[dev, loc]\n'> <'\n'> <'\t\t\tif (opt_start)\n'> 
              <'\t\t\t\tprintf "%-15s ", starts[dev, loc]\n'> <'\t\t\tif (opt_end)\n'> <'\t\t\t\tprintf "%-15s ", time\n'> 
              <'\t\t\tprintf "%-12.12s %-6s %-4s %-8s %-12s %-6s %8s\\n",\n'> <'\t\t\t    comm, pid, dir, dev, loc, nsec * 512, latency\n'> <'\t\t\tif (!opt_duration)\n'> 
              <'\t\t\t\tfflush()\n'> <'\n'> <'\t\t\tdelete starts[dev, loc]\n'> <'\t\t\tdelete comms[dev, loc]\n'> 
              <'\t\t\tdelete pids[dev, loc]\n'> <'\t\t}\n'> <'\t\tnext\n'> <'\t}\n'> <'\n'> 
              <'\t$0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" }\n'>
            )
          }
        )
      ]
      negated: F
      stderr_indices: []
    )
    (C {<end>})
  ]
)