Receiving an Integer command line argument

Question

I'm writing a program that takes a single command line argument. This argument needs to be in the range [0, INT_MAX]. What is the best way to take argv[1] and convert it into an int, while ensuring that it will be a valid integer?

possible duplicate of [convert string to integer sscanf or atoi](http://stackoverflow.com/questions/3420629/convert-string-to-integer-sscanf-or-atoi) — karlphillip, Apr 25 '11 at 02:24

score 4 · Accepted Answer · answered Apr 25 '11 at 02:15

4

argv[1] is the first commandline arg and strtoul() converts to an unsigned integer

Also argc is the number of arguments, so check it is at least 2 (argc counts the program name) before calling argv[1]

Strictly strtoul() is c++ but most c compilers support it in their standard library, it takes a 'c' style char * string

answered Apr 25 '11 at 02:15

Martin Beckett

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I think you meant, "arg 0 is the program name". – Chris Jester-Young Apr 25 '11 at 02:17
@the first arg as far as argc is concerned is the program name - will try and make it clear – Martin Beckett Apr 25 '11 at 02:18
`int number = 0; sscanf(argv[1], "%d", &number);` – karlphillip Apr 25 '11 at 02:25
`strtoul()` was in C89 before it was in C++. If you're being really thorough, you'd have to check rather carefully for the error returns from any of the `strtoX()` families of functions, probably using a wrapper function. – Jonathan Leffler Apr 25 '11 at 02:29

Receiving an Integer command line argument

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