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I'm trying to call a self-defined function funk_a in strace but it doesn't seem to find it. I confirmed that funk_a can be called by itself. I appreciate any opinions. 

$ source ./strace_sample.sh $ funk_a Earth, Wind, Fire and Water $ funk_b Get on up strace: Can't stat 'funk_a': No such file or directory $ dpkg -p strace|grep Vers Version: 4.8-1ubuntu5 $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 14.04.5 LTS Release: 14.04 Codename: trusty

strace_sample.sh

#!/bin/bash function funk_a { echo "Earth, Wind, Fire and Water" } function funk_b { echo "Get on up" strace -o trace_output.txt -c -Ttt funk_a }

Thank you.

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  • what is the output of type funk_a? Commented Jan 22, 2017 at 11:34

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strace can only strace executable files.

funk_a is a function, a programming construct of the shell, not something you can execute.

The only thing strace could strace would be a new shell that evalutes the body of that function like:

strace -o trace_output.txt -Ttt bash -c "$(typeset -f funk_a); funk_a"

(I removed -c as it makes no sense with -Ttt).

But you'll then see all the system called made by bash to load and initialise (and after to clean-up and exit) in addition to that one write system call made by that funk_a function.

Or you could tell strace to trace the pid of the shell while it evaluates the funk_a function:

strace -o trace_output.txt -Ttt -p "$$" & funk_a kill "$!"

Though, by the time strace attaches to the PID of the shell, the shell could very well have finished interpreting the function. You could try some synchronisation like

strace -o trace_output.txt -Ttt -p "$$" & tail -F trace_output.txt | read # wait for some output in trace_output.txt funk_a kill "$!"

But even then depending on timing, trace_output.txt would include some of the system calls used interpret tail|read, or kill could kill strace before it has had the time to write the trace for the echo command to the output file.

A better approach could be to wrap the call to funk_a between two recognisable system calls like

strace -fo >(sed -n '1,\|open("///dev/null|d \|open("/dev///null|q;p' > trace_output.txt ) -Ttt -p "$$" & sleep 1 # give enough time for strace to start exec 3< ///dev/null # start signal funk_a exec 3< /dev///null # end signal
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Figured out by myself after finding out in this thread that strace can only call an executable.

Changing my example above as follows worked.

util.sh

#!/bin/bash echo "Earth, Wind, Fire and Water"

strace_sample.sh

#!/bin/bash function funk_b { echo "Get on up" #strace -o funk_a.out -c -Ttt funk_a strace -o util.out -c -Ttt ./util.sh }

Result

$ funk_b Get on up Earth, Wind, Fire and Water $ more util.out % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 0.00 0.000000 0 7 read 0.00 0.000000 0 1 write 0.00 0.000000 0 27 18 open :
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