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      ]
    )
    (command.If
      arms: [
        (if_arm
          cond: [
            (command.Sentence
              child: 
                (command.DParen
                  child: 
                    (arith_expr.VarRef
                      token: (Token id:Id.Lit_ArithVarLike val:opt_device span_id:795)
                    )
                )
              terminator: (Token id:Id.Op_Semi val:';' span_id:799)
            )
          ]
          action: [
            (command.AndOr
              ops: [Id.Op_DAmp]
              children: [
                (command.DBracket
                  expr: 
                    (bool_expr.Binary
                      op_id: Id.BoolBinary_GlobNEqual
                      left: {(DQ ($ Id.VSub_DollarName '$filter'))}
                      right: {(DQ )}
                    )
                )
                (command.ShAssignment
                  pairs: [
                    (assign_pair
                      lhs: (sh_lhs_expr.Name name:filter)
                      op: assign_op.Equal
                      rhs: {(DQ ($ Id.VSub_DollarName '$filter') (' && '))}
                      spids: [819]
                    )
                  ]
                )
              ]
            )
            (command.ShAssignment
              pairs: [
                (assign_pair
                  lhs: (sh_lhs_expr.Name name:filter)
                  op: assign_op.Equal
                  rhs: {(DQ (${ Id.VSub_Name filter) ('dev == ') ($ Id.VSub_DollarName '$dev'))}
                  spids: [826]
                )
              ]
            )
          ]
          spids: [791 801]
        )
      ]
    )
    (command.If
      arms: [
        (if_arm
          cond: [
            (command.Sentence
              child: 
                (command.DParen
                  child: 
                    (arith_expr.Binary
                      op_id: Id.Arith_DPipe
                      left: 
                        (arith_expr.VarRef
                          token: (Token id:Id.Lit_ArithVarLike val:opt_iotype span_id:841)
                        )
                      right: 
                        (arith_expr.VarRef
                          token: (Token id:Id.Lit_ArithVarLike val:opt_device span_id:845)
                        )
                    )
                )
              terminator: (Token id:Id.Op_Semi val:';' span_id:849)
            )
          ]
          action: [
            (command.If
              arms: [
                (if_arm
                  cond: [
                    (command.AndOr
                      ops: [Id.Op_DPipe]
                      children: [
                        (command.Pipeline
                          children: [
                            (command.Simple
                              words: [{(echo)} {(DQ ($ Id.VSub_DollarName '$filter'))}]
                              redirects: [
                                (redir.Redir
                                  op: (Token id:Id.Redir_Great val:'>' span_id:864)
                                  fd: -1
                                  arg_word: 
                                    {(events/block/) ($ Id.VSub_DollarName '$b_start') (/filter)}
                                )
                              ]
                            )
                          ]
                          negated: T
                        )
                        (command.Pipeline
                          children: [
                            (command.Simple
                              words: [{(echo)} {(DQ ($ Id.VSub_DollarName '$filter'))}]
                              redirects: [
                                (redir.Redir
                                  op: (Token id:Id.Redir_Great val:'>' span_id:882)
                                  fd: -1
                                  arg_word: {(events/block/block_rq_complete/filter)}
                                )
                              ]
                            )
                          ]
                          negated: T
                        )
                      ]
                    )
                  ]
                  action: [(C {(edie)} {(DQ ('ERROR: setting -d or -t filter. Exiting.'))})]
                  spids: [854 887]
                )
              ]
            )
          ]
          spids: [837 851]
        )
      ]
    )
    (command.If
      arms: [
        (if_arm
          cond: [
            (command.Sentence
              child: 
                (command.AndOr
                  ops: [Id.Op_DPipe]
                  children: [
                    (command.Pipeline
                      children: [
                        (command.Simple
                          words: [{(echo)} {(1)}]
                          redirects: [
                            (redir.Redir
                              op: (Token id:Id.Redir_Great val:'>' span_id:909)
                              fd: -1
                              arg_word: {(events/block/) ($ Id.VSub_DollarName '$b_start') (/enable)}
                            )
                          ]
                        )
                      ]
                      negated: T
                    )
                    (command.Pipeline
                      children: [
                        (command.Simple
                          words: [{(echo)} {(1)}]
                          redirects: [
                            (redir.Redir
                              op: (Token id:Id.Redir_Great val:'>' span_id:925)
                              fd: -1
                              arg_word: {(events/block/block_rq_complete/enable)}
                            )
                          ]
                        )
                      ]
                      negated: T
                    )
                  ]
                )
              terminator: (Token id:Id.Op_Semi val:';' span_id:928)
            )
          ]
          action: [(C {(edie)} {(DQ ('ERROR: enabling block I/O tracepoints. Exiting.'))})]
          spids: [901 930]
        )
      ]
    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:etext)
          op: assign_op.Equal
          rhs: (word.Empty)
          spids: [941]
        )
      ]
    )
    (command.AndOr
      ops: [Id.Op_DAmp]
      children: [
        (command.DParen
          child: 
            (arith_expr.Unary
              op_id: Id.Arith_Bang
              child: 
                (arith_expr.VarRef
                  token: (Token id:Id.Lit_ArithVarLike val:opt_count span_id:946)
                )
            )
        )
        (command.ShAssignment
          pairs: [
            (assign_pair
              lhs: (sh_lhs_expr.Name name:etext)
              op: assign_op.Equal
              rhs: {(DQ (' Ctrl-C to end.'))}
              spids: [953]
            )
          ]
        )
      ]
    )
    (C {(echo)} 
      {
        (DQ ('Tracing block I/O. Output every ') ($ Id.VSub_DollarName '$interval') (' seconds.') 
          ($ Id.VSub_DollarName '$etext')
        )
      }
    )
    (command.ShAssignment
      pairs: [
        (assign_pair
          lhs: (sh_lhs_expr.Name name:offset)
          op: assign_op.Equal
          rhs: 
            {
              (command_sub
                left_token: (Token id:Id.Left_DollarParen val:'$(' span_id:990)
                command_list: 
                  (command.CommandList
                    children: [
                      (C {($ Id.VSub_DollarName '$awk')} 
                        {
                          (SQ (Token id:Id.Lit_Chars val:'BEGIN { o = 0; }\n' span_id:994) 
                            (Token
                              id: Id.Lit_Chars
                              val: '\t$1 == "#" && $2 ~ /TASK/ && NF == 6 { o = 1; }\n'
                              span_id: 995
                            ) (Token id:Id.Lit_Chars val:'\t$2 ~ /TASK/ { print o; exit }' span_id:996)
                          )
                        } {(trace)}
                      )
                    ]
                  )
              )
            }
          spids: [989]
        )
      ]
    )
    (C {(warn)} {(DQ ('echo > trace'))})
    (command.ShAssignment
      pairs: [(assign_pair lhs:(sh_lhs_expr.Name name:i) op:assign_op.Equal rhs:{(0)} spids:[1012])]
    )
    (command.Pipeline
      children: [
        (command.WhileUntil
          keyword: (Token id:Id.KW_While val:while span_id:1015)
          cond: [
            (command.Sentence
              child: 
                (command.DParen
                  child: 
                    (arith_expr.Binary
                      op_id: Id.Arith_DPipe
                      left: 
                        (arith_expr.Unary
                          op_id: Id.Arith_Bang
                          child: 
                            (arith_expr.VarRef
                              token: (Token id:Id.Lit_ArithVarLike val:opt_count span_id:1020)
                            )
                        )
                      right: 
                        (arith_expr.Binary
                          op_id: Id.Arith_Less
                          left: 
                            (arith_expr.VarRef
                              token: (Token id:Id.Lit_ArithVarLike val:i span_id:1025)
                            )
                          right: 
                            (arith_expr.VarRef
                              token: (Token id:Id.Lit_ArithVarLike val:count span_id:1029)
                            )
                        )
                    )
                )
              terminator: (Token id:Id.Op_Semi val:';' span_id:1034)
            )
          ]
          body: 
            (command.DoGroup
              children: [
                (command.DParen
                  child: 
                    (arith_expr.UnaryAssign
                      op_id: Id.Node_PostDPlus
                      child: (sh_lhs_expr.Name name:i)
                    )
                )
                (C {(sleep)} {($ Id.VSub_DollarName '$interval')})
                (command.If
                  arms: [
                    (if_arm
                      cond: [
                        (command.Sentence
                          child: 
                            (command.DBracket
                              expr: (bool_expr.Unary op_id:Id.BoolUnary_x child:{(snapshot)})
                            )
                          terminator: (Token id:Id.Op_Semi val:';' span_id:1067)
                        )
                      ]
                      action: [
                        (command.Simple
                          words: [{(echo)} {(1)}]
                          redirects: [
                            (redir.Redir
                              op: (Token id:Id.Redir_Great val:'>' span_id:1076)
                              fd: -1
                              arg_word: {(snapshot)}
                            )
                          ]
                        )
                        (command.Simple
                          words: [{(echo)}]
                          redirects: [
                            (redir.Redir
                              op: (Token id:Id.Redir_Great val:'>' span_id:1083)
                              fd: -1
                              arg_word: {(trace)}
                            )
                          ]
                        )
                        (C {(cat)} {(snapshot)})
                      ]
                      spids: [1058 1069]
                    )
                  ]
                  else_action: [
                    (C {(cat)} {(trace)})
                    (command.Simple
                      words: [{(echo)}]
                      redirects: [
                        (redir.Redir
                          op: (Token id:Id.Redir_Great val:'>' span_id:1103)
                          fd: -1
                          arg_word: {(trace)}
                        )
                      ]
                    )
                  ]
                )
                (command.AndOr
                  ops: [Id.Op_DAmp]
                  children: [
                    (command.DParen
                      child: 
                        (arith_expr.VarRef
                          token: (Token id:Id.Lit_ArithVarLike val:opt_timestamp span_id:1114)
                        )
                    )
                    (C {(printf)} {(DQ ('time %(%H:%M:%S)T:') (Id.Lit_Other '\\') (n))} {(-1)})
                  ]
                )
                (C {(echo)} {(DQ (tick))})
              ]
            )
        )
        (C {($ Id.VSub_DollarName '$awk')} {(-v)} 
          {(Id.Lit_VarLike 'o=') ($ Id.VSub_DollarName '$offset')} {(-v)} {(Id.Lit_VarLike 'opt_timestamp=') ($ Id.VSub_DollarName '$opt_timestamp')} {(-v)} 
          {(Id.Lit_VarLike 'b_start=') ($ Id.VSub_DollarName '$b_start')} 
          {
            (SQ (Token id:Id.Lit_Chars val:'\n' span_id:1161) 
              (Token
                id: Id.Lit_Chars
                val: '\tfunction star(sval, smax, swidth) {\n'
                span_id: 1162
              ) (Token id:Id.Lit_Chars val:'\t\tstars = ""\n' span_id:1163) 
              (Token id:Id.Lit_Chars val:'\t\tif (smax == 0) return ""\n' span_id:1164) (Token id:Id.Lit_Chars val:'\t\tfor (si = 0; si < (swidth * sval / smax); si++) {\n' span_id:1165) 
              (Token id:Id.Lit_Chars val:'\t\t\tstars = stars "#"\n' span_id:1166) (Token id:Id.Lit_Chars val:'\t\t}\n' span_id:1167) 
              (Token id:Id.Lit_Chars val:'\t\treturn stars\n' span_id:1168) (Token id:Id.Lit_Chars val:'\t}\n' span_id:1169) (Token id:Id.Lit_Chars val:'\n' span_id:1170) 
              (Token id:Id.Lit_Chars val:'\tBEGIN { max_i = 0 }\n' span_id:1171) (Token id:Id.Lit_Chars val:'\n' span_id:1172) 
              (Token id:Id.Lit_Chars val:'\t# common fields\n' span_id:1173) (Token id:Id.Lit_Chars val:'\t$1 != "#" {\n' span_id:1174) 
              (Token
                id: Id.Lit_Chars
                val: '\t\ttime = $(3+o); sub(":", "", time)\n'
                span_id: 1175
              ) (Token id:Id.Lit_Chars val:'\t\tdev = $(5+o)\n' span_id:1176) 
              (Token id:Id.Lit_Chars val:'\t}\n' span_id:1177) (Token id:Id.Lit_Chars val:'\n' span_id:1178) 
              (Token id:Id.Lit_Chars val:'\t# block I/O request\n' span_id:1179) (Token id:Id.Lit_Chars val:'\t$1 != "#" && $0 ~ b_start {\n' span_id:1180) 
              (Token id:Id.Lit_Chars val:'\t\t#\n' span_id:1181) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t# example: (fields1..4+o) 202,1 W 0 () 12862264 + 8 [tar]\n'
                span_id: 1182
              ) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t# The cmd field "()" might contain multiple words (hex),\n'
                span_id: 1183
              ) (Token id:Id.Lit_Chars val:'\t\t# hence stepping from the right (NF-3).\n' span_id:1184) 
              (Token id:Id.Lit_Chars val:'\t\t#\n' span_id:1185) (Token id:Id.Lit_Chars val:'\t\tloc = $(NF-3)\n' span_id:1186) 
              (Token id:Id.Lit_Chars val:'\t\tstarts[dev, loc] = time\n' span_id:1187) (Token id:Id.Lit_Chars val:'\t\tnext\n' span_id:1188) (Token id:Id.Lit_Chars val:'\t}\n' span_id:1189) 
              (Token id:Id.Lit_Chars val:'\n' span_id:1190) (Token id:Id.Lit_Chars val:'\t# block I/O completion\n' span_id:1191) 
              (Token
                id: Id.Lit_Chars
                val: '\t$1 != "#" && $0 ~ /rq_complete/ {\n'
                span_id: 1192
              ) (Token id:Id.Lit_Chars val:'\t\t#\n' span_id:1193) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t# example: (fields1..4+o) 202,1 W () 12862256 + 8 [0]\n'
                span_id: 1194
              ) (Token id:Id.Lit_Chars val:'\t\t#\n' span_id:1195) 
              (Token id:Id.Lit_Chars val:'\t\tdir = $(6+o)\n' span_id:1196) (Token id:Id.Lit_Chars val:'\t\tloc = $(NF-3)\n' span_id:1197) 
              (Token id:Id.Lit_Chars val:'\n' span_id:1198) (Token id:Id.Lit_Chars val:'\t\tif (starts[dev, loc] > 0) {\n' span_id:1199) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t\tlatency_ms = 1000 * (time - starts[dev, loc])\n'
                span_id: 1200
              ) (Token id:Id.Lit_Chars val:'\t\t\ti = 0\n' span_id:1201) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t\tfor (ms = 1; latency_ms > ms; ms *= 2) { i++ }\n'
                span_id: 1202
              ) (Token id:Id.Lit_Chars val:'\t\t\thist[i]++\n' span_id:1203) 
              (Token id:Id.Lit_Chars val:'\t\t\tif (i > max_i)\n' span_id:1204) (Token id:Id.Lit_Chars val:'\t\t\t\tmax_i = i\n' span_id:1205) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t\tdelete starts[dev, loc]\n'
                span_id: 1206
              ) (Token id:Id.Lit_Chars val:'\t\t}\n' span_id:1207) 
              (Token id:Id.Lit_Chars val:'\t\tnext\n' span_id:1208) (Token id:Id.Lit_Chars val:'\t}\n' span_id:1209) (Token id:Id.Lit_Chars val:'\n' span_id:1210) 
              (Token id:Id.Lit_Chars val:'\t# timestamp\n' span_id:1211) (Token id:Id.Lit_Chars val:'\t$1 == "time" {\n' span_id:1212) 
              (Token id:Id.Lit_Chars val:'\t\tlasttime = $2\n' span_id:1213) (Token id:Id.Lit_Chars val:'\t}\n' span_id:1214) (Token id:Id.Lit_Chars val:'\n' span_id:1215) 
              (Token id:Id.Lit_Chars val:'\t# print summary\n' span_id:1216) (Token id:Id.Lit_Chars val:'\t$1 == "tick" {\n' span_id:1217) 
              (Token id:Id.Lit_Chars val:'\t\tprint ""\n' span_id:1218) (Token id:Id.Lit_Chars val:'\t\tif (opt_timestamp)\n' span_id:1219) 
              (Token id:Id.Lit_Chars val:'\t\t\tprint lasttime\n' span_id:1220) (Token id:Id.Lit_Chars val:'\n' span_id:1221) 
              (Token id:Id.Lit_Chars val:'\t\t# find max value\n' span_id:1222) (Token id:Id.Lit_Chars val:'\t\tmax_v = 0\n' span_id:1223) 
              (Token
                id: Id.Lit_Chars
                val: '\t\tfor (i = 0; i <= max_i; i++) {\n'
                span_id: 1224
              ) (Token id:Id.Lit_Chars val:'\t\t\tif (hist[i] > max_v)\n' span_id:1225) 
              (Token id:Id.Lit_Chars val:'\t\t\t\tmax_v = hist[i]\n' span_id:1226) (Token id:Id.Lit_Chars val:'\t\t}\n' span_id:1227) (Token id:Id.Lit_Chars val:'\n' span_id:1228) 
              (Token id:Id.Lit_Chars val:'\t\t# print histogram\n' span_id:1229) 
              (Token
                id: Id.Lit_Chars
                val: '\t\tprintf "%8s .. %-8s: %-8s |%-38s|\\n", ">=(ms)", "<(ms)",\n'
                span_id: 1230
              ) (Token id:Id.Lit_Chars val:'\t\t    "I/O", "Distribution"\n' span_id:1231) 
              (Token id:Id.Lit_Chars val:'\t\tms = 1\n' span_id:1232) (Token id:Id.Lit_Chars val:'\t\tfrom = 0\n' span_id:1233) 
              (Token
                id: Id.Lit_Chars
                val: '\t\tfor (i = 0; i <= max_i; i++) {\n'
                span_id: 1234
              ) (Token id:Id.Lit_Chars val:'\t\t\tprintf "%8d -> %-8d: %-8d |%-38s|\\n", from, ms,\n' span_id:1235) 
              (Token
                id: Id.Lit_Chars
                val: '\t\t\t    hist[i], star(hist[i], max_v, 38)\n'
                span_id: 1236
              ) (Token id:Id.Lit_Chars val:'\t\t\tfrom = ms\n' span_id:1237) 
              (Token id:Id.Lit_Chars val:'\t\t\tms *= 2\n' span_id:1238) (Token id:Id.Lit_Chars val:'\t\t}\n' span_id:1239) 
              (Token id:Id.Lit_Chars val:'\t\tfflush()\n' span_id:1240) (Token id:Id.Lit_Chars val:'\t\tdelete hist\n' span_id:1241) 
              (Token
                id: Id.Lit_Chars
                val: '\t\tdelete starts\t# invalid if events missed between snapshots\n'
                span_id: 1242
              ) (Token id:Id.Lit_Chars val:'\t\tmax_i = 0\n' span_id:1243) 
              (Token id:Id.Lit_Chars val:'\t}\n' span_id:1244) (Token id:Id.Lit_Chars val:'\n' span_id:1245) 
              (Token
                id: Id.Lit_Chars
                val: '\t$0 ~ /LOST.*EVENTS/ { print "WARNING: " $0 > "/dev/stderr" }\n'
                span_id: 1246
              )
            )
          }
        )
      ]
      negated: F
    )
    (C {(end)})
  ]
)