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                      here_end_span_id: 269
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                        <'                 -d seconds      # trace duration, and use buffers\n'>
                        <'                 -h              # this usage message\n'>
                        <'                 -H              # include column headers\n'>
                        <'                 -p PID          # trace when this pid is on-CPU\n'>
                        <'                 -L TID          # trace when this thread is on-CPU\n'>
                        <'  eg,\n'>
                        <'       functrace do_nanosleep    # trace the do_nanosleep() function\n'>
                        <'       functrace \'*sleep\'        # trace functions ending in '>
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                        <sleep>
                        <Id.Right_DoubleQuote '"'>
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                        <Id.Right_DoubleQuote '"'>
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                        <'       functrace \'tcp*\' > out    # trace all '>
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                        <Id.Right_DoubleQuote '"'>
                        <' funcs to out file\n'>
                        <
'       functrace -d 1 \'tcp*\' > out  # trace 1 sec, then write out file\n'
                        >
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                        <'See the man page and example file for more info.\n'>
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            (C {<warn>} {(DQ <'echo > set_ftrace_filter'>)})
            (C {<warn>} {(DQ <'echo > trace'>)})
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            (command.Simple
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        (word_part.ArithSub
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        (C {<edie>} {(DQ <'ERROR: You can use -p or -L but not both.'>)})
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          action: [
            (C {<echo>} 
              {
                (DQ <'Tracing '> (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'>) 
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            (DQ <'Tracing '> (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'>) 
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    (command.AndOr
      ops: [Id.Op_DPipe]
      children: [
        (C {<cd>} {($ Id.VSub_DollarName '$tracing')})
        (C {<die>} 
          {
            (DQ <'ERROR: accessing tracing. Root user? Kernel has FTRACE?\n'> 
              <'    debugfs mounted? (mount -t debugfs debugfs /sys/kernel/debug)'>
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    )
    (command.AndOr
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        (C {<die>} 
          {
            (DQ <'ERROR: ftrace may be in use by PID '> 
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    )
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        (command.Simple
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          do_fork: T
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        (C {<die>} {(DQ <'ERROR: unable to write '> ($ Id.VSub_DollarName '$flock') <.>)})
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    )
    (command.ShAssignment
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      redirects: [(redir op:<Id.Redir_Less '<'> loc:(redir_loc.Fd fd:0) arg:{<current_tracer>})]
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        (command.DBracket
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                          action: [
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                              {
                                (DQ <'ERROR: setting -p '> ($ Id.VSub_DollarName '$pid') 
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                      {
                        (DQ <'ERROR: setting -L '> ($ Id.VSub_DollarName '$tid') 
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                (DQ <'ERROR: enabling '> (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'>) 
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                      children: [
                        (command.Simple
                          words: [{<echo>} {<Id.KW_Function function>}]
                          redirects: [
                            (redir
                              op: <Id.Redir_Great '>'>
                              loc: (redir_loc.Fd fd:1)
                              arg: {<current_tracer>}
                            )
                          ]
                          do_fork: T
                        )
                      ]
                      negated: T
                    )
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (C {<edie>} 
              {
                (DQ <'ERROR: setting current_tracer to '> 
                  (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'>) <function> (word_part.EscapedLiteral token:<Id.Lit_EscapedChar '\\"'>) <'. Exiting.'>
                )
              }
            )
          ]
          spids: [948 961]
        )
      ]
    )
    (C {<warn>} {(DQ <'echo > trace'>)})
    (command.If
      arms: [
        (if_arm
          cond: 
            (condition.Shell
              commands: [
                (command.Sentence
                  child: (command.DParen child:<Id.Lit_ArithVarLike opt_duration>)
                  terminator: <Id.Op_Semi _>
                )
              ]
            )
          action: [
            (C {<sleep>} {($ Id.VSub_DollarName '$duration')})
            (command.If
              arms: [
                (if_arm
                  cond: 
                    (condition.Shell
                      commands: [
                        (command.Sentence
                          child: (command.DParen child:<Id.Lit_ArithVarLike opt_headers>)
                          terminator: <Id.Op_Semi _>
                        )
                      ]
                    )
                  action: [(C {<cat>} {<trace>})]
                  spids: [1004 1014]
                )
              ]
              else_action: [(C {<grep>} {<-v>} {(SQ <'^#'>)} {<trace>})]
            )
          ]
          spids: [986 996]
        )
      ]
      else_action: [
        (command.AndOr
          ops: [Id.Op_DAmp]
          children: [(command.DParen child:<Id.Lit_ArithVarLike opt_headers>) (C {<cat>} {<trace>})]
        )
        (C {<cat>} {<trace_pipe>})
      ]
    )
    (C {<end>})
  ]
)