TeX’s job name

When you run pdflatex options argument, if argument does not start with a backslash then TeX considers it the name of a file to input. Otherwise it waits for the first \input instruction and the name of the input file will be the job name. This is used to name the log file the output file. The jobname option overrides that process and directly specifies the name. See Command line input, for an example of its use.

pdflatex -jobname=aa "\RequirePackage[draft]{graphicx}\input{aa.tex}"

The jobname option is there because otherwise the output file would be graphicx.pdf, as \RequirePackage does an \input of its own.