Why argv

I could write a command line interface, which might be kind of nice, but the end product is going to be an HTML file, so the terminal window is ultimately going to get in the way.

However, we can make a binary, include some ARGV parsing to grab the query and options, and use the command line to directly launch the process which, I might add, is time consuming, perfect as a background task. There we go. That first line is important for binaries.

Right now it will blow up, because query, range, and display will be set to nil. I want a user to be able to just specify a query and nothing else. It will mostly work as intended. We can build the gem, install it, and run it from the command line. JerryCoffin, one might also point out that even if the actual arguments were contiguous in memory, they can have arbitrary lengths, so one would still need distinct pointers for each of them to be able to access argv[i] without scanning through all the previous ones.

Show 12 more comments. DanielWagner: Yes, this is from C's Unix heritage. On Linux, argv[] the array itself and argc are on the stack on process entry. I assume most Unixes are the same, because that's a good place for it. Following the letter of the standard is not sufficient to be useful ; it intentionally leaves a lot of room for implementation choices. Although some Windows programs will want to treat quotes specially, so real implementations do provide a way to get the flat string, too.

Add a comment. To illustrate:. Erik Eidt Erik Eidt 31k 4 4 gold badges 50 50 silver badges 80 80 bronze badges. Sure, it can be made to work, and as I said, an unusual construct. In this case that's argv[3] , not argv[4]. Hill, yes, thank you as I was trying to be explicit about the null character terminators and missed that one. Show 4 more comments. Basile Starynkevitch Basile Starynkevitch To quote C99 standard : — If the value of argc is greater than zero, the array members argv[0] through argv[argc-1] inclusive shall contain pointers to strings , which are given implementation-defined values by the host environment prior to program startup.

Sergiy Kolodyazhnyy Sergiy Kolodyazhnyy 4 4 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. By storing a different string there, a program can change which files are read. Use "-" to represent the standard input. Storing additional elements and incrementing ARGC causes additional files to be read. If the value of ARGC is decreased, that eliminates input files from the end of the list. Asked 7 years, 9 months ago.

Active 5 months ago. Viewed 6k times. I am a beginner and please explain it high level perspective. Improve this question. Jonathan Leffler k gold badges silver badges bronze badges. What I meant is what is the need for a pointer there. I was talking to a friend about your second question last night actually - what I said was that it could be needed if the user changes the name of the program, we might need to know what it's now called, say to call another instance, update, etc.

Show 2 more comments. Active Oldest Votes. Improve this answer. Keith Thompson Keith Thompson k 39 39 gold badges silver badges bronze badges. Add a comment. Shahbaz Shahbaz KeithThompson, I made the wording more precise. JonathanLeffler, exactly. However, in the couple of times that I actually wrote vi instead of vim , I didn't see any difference, that's why I said: As far as I know, neither of the programs I mentioned above actually do this with respect to vim and vi — Shahbaz.

The entity that calls main isn't necessarily even written in C. An array expression decays to a pointer to its first element, but there isn't necessarily any array expression. There are two distinct rules at play: a parameter of array type is adjusted to a parameter of pointer type at compile time, and an expression of array type is converted "decays" to a pointer value, notionally at run time.

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