Despite popular belief, there is a scholarly consensus that ‘satan’ in the book of Job is not a personal name, and does not refer to the supernatural evil being known as ‘Satan’ or ‘the devil’.
‘The appearance of “Satan” in virtually all English translations of the book of Job befuddles me since it is very clear that Satan was never in the book of Job to begin with! While almost every English translation of the book of Job will refer to “Satan” in the first couple chapters of the book, there is scholarly consensus that this is certainly not what the Hebrew original is referring to!’
‘What is the character and function of this member of the “sons of God,” the “Satan”? We note first that the definite article appears before the term at each of its occurrences in the book (1:6, 7 bis, 8, 9, 12 bis; 2:1, 2 bis, 3, 4, 6, 7); this fact prevents us from identifying the figure of the Satan with “Satan” of later Jewish and Christian theology.'
Most commentators now suggest that ‘satan’ should be translated ‘adversary’, and that it refers in Job to an angel testing Job, or a mortal man who was jealous of him. 
Note that “Who is Satan in Job 1?” is probably not the most important question about the Satan in Job 1. The most important question is “What is Job 1?”.
 Williams, ‘The Mysterious Appearance of “Satan” in English Translations of the Book of Job’, blog post 26th March, 2008.
 Clines, ‘Job 1-20’, Word Biblical Commentary, pp. 19-20 (2002).
 ‘In Job we see Satan as one of the “sons of God” who tests men’s claims to be religious. He does not appear to be evil so much as he is skeptical of religious pretensions. The testing of Job is Satan’s idea, since testing people is his job. The destruction he carries out against Job is not in opposition to God, but rather is done with divine approval. In doing so he operates within his role as God’s servant. Job would, if he knew the plot hatched in heaven against him, consider Satan the worst sort of enemy. All of this is to say that “the Satan” in the Book of Job cannot be entirely identified with “the Devil” or “Satan” in the New Testament.’, Reyburn, ‘A Handbook on the Book of Job’, UBS Handbook Series, p. 39 (1992).
 ‘For a number of reasons, grammatical and theological, many scholars question whether or not the character introduced here should be identified with the “Devil” of later Scripture. They see him as one of the angels (“sons of God”) who regularly came before the Lord. Rather than God’s enemy they understand him to be God’s agent, whose specific duty it is to expose any disloyalty among God’s subjects.’, Hooks, ‘Job’, College Press NIV Commentary, p. 62 (2006).