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9.8. Formatting functions
The following functions help you format output.
9.8.1. ctime
General syntax:
ctime:string(epochsecs:long)
This function accepts an argument of seconds since the epoch as returned by
gettimeofday_s(). It returns a date string in UTC of the form:
"Wed Jun 30 21:49:008 2006"
This function does not adjust for timezones. The returned time is always in GMT. Your script must manually adjust epochsecs before passing it to ctime() if you want to print local time.
9.8.2. errno_str
General syntax:
errno_str:string (err:long)
This function returns the symbolic string associated with the given error code, such as ENOENT for the number 2, or E#3333 for an out-of-range value such as 3333.
9.8.3. returnstr
General syntax:
returnstr:string (returnp:long)
This function is used by the syscall tapset, and returns a string. Set returnp equal to 1 for decimal, or 2 for hex.
9.8.4. thread_indent
General syntax:
thread_indent:string (delta:long)
This function returns a string with appropriate indentation for a thread. Call it with a small positive or matching negative delta. If this is the outermost, initial level of indentation, then the function resets the relative timestamp base to zero.
The following example uses thread_indent() to trace the functions called in the drivers/usb/core kernel source. It prints a relative timestamp and the name and ID of the current process, followed by the appropriate indent and the function name. Note that "swapper(0)" indicates the kernel is running in interrupt context and there is no valid current process.
probe kernel.function("*@drivers/usb/core/*") {
printf ("%s -> %s\n", thread_indent(1), probefunc())
}
probe kernel.function("*@drivers/usb/core/*").return {
printf ("%s <- %s\n", thread_indent(-1), probefunc())
}
This prints:
0 swapper(0): -> usb_hcd_irq 8 swapper(0): <- usb_hcd_irq 0 swapper(0): -> usb_hcd_irq 10 swapper(0): -> usb_hcd_giveback_urb 16 swapper(0): -> urb_unlink 22 swapper(0): <- urb_unlink 29 swapper(0): -> usb_free_urb 35 swapper(0): <- usb_free_urb 39 swapper(0): <- usb_hcd_giveback_urb 45 swapper(0): <- usb_hcd_irq 0 usb-storage(1338): -> usb_submit_urb 6 usb-storage(1338): -> usb_hcd_submit_urb 12 usb-storage(1338): -> usb_get_urb 18 usb-storage(1338): <- usb_get_urb 25 usb-storage(1338): <- usb_hcd_submit_urb 29 usb-storage(1338): <- usb_submit_urb 0 swapper(0): -> usb_hcd_irq 7 swapper(0): <- usb_hcd_irq
