I am trying to read 12|11|13 from command line from my application.
I get error "11 is not recognozed as an internal command" while reading this string.
I am OK if I can read complete string or individual numbers.
Can anyone suggest how to read this?
Nipun
You need to pass the args between quotes ex :
myprog "11|12|14"
Because if you don't, the caracter | (pipe) is used to pass the output from the program on left to the program on right of the symbol.
Related
I'm writing a brainfuck interpreter in NASM, where code is supplied as a command line argument to the program. I'm trying to test looping, but GDB doesn't like my input. For example, this executes error-free when run on its own:
$./interpret "+++++[->+<]"
It hangs indefinitely, but I think that that's due to a bug in the looping logic in the interpreter (thus GDB).
If I load interpret into GDB though and attempt to supply the same argument, I get complaints:
gef➤ start "+++++[->+<]"
/bin/bash: line 1: ]: No such file or directory
/bin/bash: line 1: ]: No such file or directory
This seems to be due to < being interpreted as redirection despite the quotes, since [] works fine in GDB.
I tried escaping the STDIN redirection with \<, but that leads to the same error, and <<, but that leads to a warning:
gef➤ start "+++++[->+<<]"
/bin/bash: line 1: warning: here-document at line 1 delimited by end-of-file (wanted `]')
And the code gets cut off:
$r15 : 0x00007fffffffe428 → 0x002d5b2b2b2b2b2b ("+++++[-"?)
Is there a way to have GDB take what I give literally to start, and not attempt to do any redirection/interpretation of the arguments?
Is there a way to have GDB take what I give literally to start, and not attempt to do any redirection/interpretation of the arguments?
GDB isn't doing any interpretation, bash does. Using single-quotes instead of double-quotes may fix that.
(I wasn't able to replicate the problem using GDB-10.0 and bash-5.1.4 with double quotes though.)
I have a small program that can ask users for some input (in essence just the gets function). Now, I want to play around with the input a little bit. I run the program with gdb and I want to insert bytes in hexadecimal format in the gdb prompt.
The way I tried to do it on the gdb command line interface is like so:
(gdb) printf "\x20\x20" | ./program
But that results in the error:
Unrecognized escape character \x in format string.
If I do the same in the shell without the gdb prompt its working. What am I doing wrong?
Thanks :)
You aren't doing anything wrong -- it is just a missing feature of gdb. You could file a bug report.
A workaround is:
(gdb) printf "%c", 0x20
I have a program I am writing, I have already completed it, but the requirement/specification for it says that:
In the "Command Prompt", if someone runs your program like this:
Peter David < savednames.txt
it should print out the names inside savednames.txt that matches each of "Peter" and "David"
I have written the program but my own is interactive, i.e it asks for the file, then the name you want to search for, and then it prints the matches.
It works perfectly fine, but I don't understand what the running of the program in command prompt like this: "Peter David < savednames.txt" means. I am using C++ on Microsoft Windows.
Please I need your help to explain it and how to implement it in my code...is it some kind of operator overloading or ...I don't understand!
On the command line, < is used for input redirection. The shell opens the file whose name follows the < and copies its contents into standard input for the program.
So if you called program input.txt, you could open the file and read its contents using std::ifstream or whatever; if you called program < input.txt, you could just read the file's contents from stdin using cin.
You can also do the same for output. Instead of opening a file and writing to it in your code, write to stdout and call your program as program > output.txt.
yourprogramname Peter David < savednames.txt
means that your program will be called with Peter as first argument, David as second argument, and its standard input will be connected to a stream reading out of savednames.txt.
You just need to read standard input one row at a time, and process it according to the arguments you received.
You just need to modify the code you already have to take the names from the command line (is there a limit? Could there be three names? Or four? You need to consider that) and to read the data from standard input stream, without any need of opening a file.
How can I save all the input(cin) and output(cout, cerr) from a program whose input is taken from file(using "<")? I would like the input and output to be in order(so each input is followed by corresponding output as if I were typing the input in myself).
I tried ">" to output everything to a file, but that only saves standard output(no input/cerr), and just plainly copying the command line output still only gives the output without the input(because of how "<" works).
Is there a way to write everything(output+input) to file in order?
EDIT: edited for clarity
EDIT2: I just realized that it's impossible to do what I'm trying to do since the console does not know anything about when the commands would actually be entered. I'll have to manually enter commands and use the "script" command to actually log all input/output.
You need to add cerr to the stream
command > file 2&>1
This means put 2 (stderr) to 1 (stdout) as well.
I need to control a program in c++ (windows), I need to call it, then pass data to it as I collect it, finally after a certain command that program will use that data.
I need to open the prog.exe and then line by line or value by value supply it information, it works manually through cmd.
I have tried system() but this will stop after I open the program.
I need something like this.
//call it
prog.exe
//add data
DataStart
Data 1 [2 34 454 5]//etc
DataEnd //the program will take it from here.
all being passed though command line
There are different ways you could do this - if your program needs to execute part of the way through your code before getting the data as input, you can just use standard input, and prompt the user to type the data. If you want to use variable values for the input, but you will know them before execution, you can pass the information as command line arguments, where you will execute like so
prog.exe 1 2 3
and your program will access the data via argv[i] where i corresponds to each command line argument.
have your program read from standard input, and from the command line 'pipe' the result of the other program to yours
eg.
datagenerator.exe | prog.exe
assuming that datagenerator.exe writes to standard output, the | character will redirect the output to prog.exe's standard input