Deal all some can help me two things

I want to cheek my RAD data mapping percentage, as I know i can do that with $ samtools flagstat (........bam file). I want to cheek all the sample with bash command and save it in a text file, how can I that?

Second, i call my snps with bcf tools, so got output as .bcf format; how can convert it to Structure format (.str) or other useful format, suggestion please,

How can I explore inside this .bcf file?

thanks a lot for your kind help and suggestion.