[FFmpeg-devel] [PATCH V4 2/2] configure: replace 'pr' with printf since busybox does not support pr

[Guo, Yejun]

> -----Original Message-----
> From: Guo, Yejun
> Sent: Wednesday, April 24, 2019 7:02 PM
> To: Guo, Yejun <yejun.guo at intel.com>
> Subject: Re: [FFmpeg-devel] [PATCH V4 2/2] configure: replace 'pr' with printf
> since busybox does not support pr
> 
> >  log_file(){
> >     log BEGIN $1
> > -    pr -n -t $1 >> $logfile
> > +    i=1
> 
> Shell variables are global. This means that any part of the code which ends
> up calling `log_file` directly or through some other function (and not isolated
> in a subshell) will get its `i` variable clobbered by `log_file`. This can be
> very tricky to debug and identify.

how about add the keyword local which makes the variables not global.

and I should also add 'local' in function print_in_columns.

> 
> Please use a variable name which is unlikely to be used by other functions,
> like `log_file_i`. Same goes for `line` below. This is critical especially in

I'll also add local keyword for line.

local line
while IFS= read -r line;do
...

> functions which end up get called by a lot of other function - like `log_file`.
> 
> > +    while read line;do
> 
> This needs to be `while IFS= read -r line; do`.
> 
> Without the IFS= part trailing white spaces will be trimmed, and without
> the -r part backslash ('\') will be interpreted an an escape char.

thanks, will change it.

> 
> > +        printf '%5s  %s\n' "${i}" "${line}"
> > +        i=$(($i+1))
> > +    done < $1 >> $logfile
> 
> While the previous version of the function used `$1` unquoted, it's generally
> a very bad practice, as it cannot handle white spaces in file names and is
> subjected to globbing and open for attacks. In general always quote _all_
> strings unless you know for a fact that it's not required. In this case it _is_
> required.

will quote $1 and $logfile

> 
> >     log END $1
> > }