I know how to get the stdout into a file using dup/dup2 system calls, but how do I get the entire output that would be normally shown on my terminal(including the prompt that says my username along with the $ symbol and the current working directory) to a file?
Yes you can, but this may be difficult in many details (depending on your expert level). For the shell to behave normally (I would mean exactly as in a terminal), then it needs to interact with a terminal (special system object). So you need to create a program that behave like a terminal, this what pseudo-terminals devices (/dev) are intended for. Read documentation about this to implement it but roughly, your application should behave like the user so should be connected to the slave side of the pseudo-terminal, and the shell to the master side of the pseudo-terminal. Then you can easily log real inputs made by the user and catch outputs made by the shell.
Can't comment cause of low reputation.
I would say there is no way to do that inside a code in C. Instead, you could use bash for example to redirect everything to a file, and leave the code in C as it is.
In this way you have all the info you want to save: prompt, current directory, call to the program (including flags), and of course the output of the program.
Well, you can do:
-For bash prompt PS1: Echo expanded PS1 (in case you want it expanded, if not there is a simple way to do it just echong PS1)
- For executed command: https://unix.stackexchange.com/questions/169259/how-to-capture-command-line-input-into-logfile-and-execute-it-at-the-same-time
- Standard output and error output: Redirect stderr and stdout in a Bash script
And that's all you want to capture, I think.
Look up the script command in Unix systems. If you want to capture all keyboard and std in/out for a command, use the script executable. If you want to see how it's done, look up the source.
Related
I am noobie with C.
I've seen system() and fork() and execv() stuff, but I do not think they are what I need ( or they just do not work )
I just want to my C program to open vim immediately of a file path to edit, then i can quit vim and the program continues, in my case it will just exit.
Think like git commit, it opens vim for me then when I save+exit it sends the commit.
Any ideas?
System(3) will do the work, but beware that if you call your program with the input/output redirected not to a terminal, this will propagate to the execution of vim and it will not work.
vim(3) requires that the input and output are directed to a terminal line, it cannot work on redirected input, so the best way to call it should be (with system()):
system("/usr/bin/vim file </dev/tty >/dev/tty");
The redirection clauses specify that the input and the output be redirected to the session controlling terminal, so you'll get it working even if you have redirected standard input/output in the main program.
system() is what I was looking for, I was using it incorrectly, but it's simple just use:
system("vim path/to/file.txt");
will open vim of current directy and work like expected ( like git commit )
Here I have one command which is like interactive mode:
obex_test -b $BD_ADDR $CH_NUM
This command is from a script but I want to run this command through a system call in a C program.
obex_test is nothing but obex file transfer library.
Here I want to receive a file from remote device to local device through bluetooth.
This is the manual page of obex_test
Please can anybody tell me how can I put my C program in interactive mode like this command, and I want to use this command also.
I used popen(command,"r") but its not useful; it does not take input from the user.
If I used "w" mode then I don't know what happens; I directly get a message like >Unknown Command. It's the error this command gives when we give different options. So it's taken something as a write mode.
You could have two pairs of pipes (created with the pipe(2) system call); one for data from your program to obex_test's stdin and one from obex_test's stdout to your program. Then you would fork and execve... Beware of deadlocks (your program blocked on writing to obex_test stdin when its output pipe is full and blocking it), you might need to call poll(2) or select(2)...
However, as it man pages explain, "obex_test is a test application for the libopenobex library". So why don't call directly functions inside this libopenobex library, which you would link to your program?
You can use the system command. Check the manual page for more details.
For e.g. system( "obex_test -b 172.16.7.1 1234" );
Basically I want to do a program almost like a keylogger. The thing is that I as network admin sometimes I don't remember what I did to a machine on certain case, or same times I make howto's and tutorials for linux. I want to record what have i done.
So basically the idea of this program is:
you type the name of the program, (I call it rat for the moment)
$ rat
Welcome everything from now on will be recorded
recording $ ls
file1 file2 file3
recording $ quit
Bye bye
Everything you do will go out to an xml file. Something like this
<?xml version='1.0' encoding='UTF-8' ?>
<rat>
<command>
<input>ls</input>
<output>file1 file2 file3</output>
<err><err>
</command>
</rat>
i am doing some tests with fp_in = popen( input, "w");
and system, but first with popen i cant change directories and with "system i cant properly manage the input and output.
I was also checking if there is something I can do to bash like a plugin but haven't find any information.
At some points if feels like it I should create another shell (which is way beyond my current abilities) or fork bash sh. But it should been that complicated right.
I am open to suggestion where to start.
I am rusty with C, so I am reading again a lot of basic stuff.
With the xml file, later i was thinking on making a program to store this data and/or editing this data so i can create tutials and howto.
I can think of many ways of expanding this up to using printscreen so all the stored images go to a file you can upload to a server (for the moment i am glad to store the data). It could be a usefull tool.
ps. I do know this can be use for evil things too.
There already exists the script command, which will record all input and output into the terminal, writing it into a transcript. I would recommend just using that, unless you have particular needs that it doesn't meet. Actually, the nicest version of script that I've seen has been the NetBSD version, so you may want to look into that if the Linux version doesn't meet your needs.
If you would like to write it yourself, instead of using system, I would recommend that you use fork/exec to create a single shell process, which you copy all input and output into. To get an idea of how this works, I'd recommend looking at the source code for an existing version of script.
Most shells have a script built-in which will simply record the text in- and out- from the command line. Not quite what you're looking for... To my surprise script is not a built in, which means it is a model for building what you want.
The script command does almost what you want: it simply records the text in- and out- from the command line.
If you make your prompt distinctive (so that you can reliably tell the difference between shell commands and everything else) you can post-process the output of script to achieve your goals. Alternately you can hack script to get it to emit the XML you're looking for.
You can also try approaching this from a different angle. Instead of using a regular shell, connect to the machine using ssh or telnet and run your commands that way. Many ssh/telnet clients (PuTTY, for instance) have an option to log all console input and output during the session. You should be able to post-process this log to generate whatever type of logfile that you need.
Depending on your setup, you might not even have to use a second machine (you should be able to ssh into yourself).
I am trying to control ftp client from C program (OS X). I did fork and execve - process is started ok. The problem is with pipes - I can send command to ftp client process and get feedback from it just fine (If i send "help\n" i get back help output) but what I never get in pipe is "ftp> " prompt. Any ideas?
Ivan
Your ftp client is probably behaving differently if stdin/stdout is a terminal or something else (lots of program do, for a start the C library does buffering in a different way...) If you want to control that, search information about pseudo-terminals, that's a little too technical to be explained here. (And looks first at programs like expect, it's possible you won't have to write yours).
A program can examine stdin to find out whether it's a terminal or a pipe. In your case, the FTP program probably does that (for example to know whether it can use escape sequences to render progress bars or offer command line editing).
If you really need the prompt, you have to look into PTYs (pseudo terminals) which emulate a console.
wild guess: isn't the "ftp>" prompt written to STDERR ?
I need to run a script and have access to the default stdin (terminal input) in my program. I could do ./program "script", opening and parsing the script through the program, but I want to make it POSIX style, accepting input from pipes or from redirection.
I mean, since my program is a parser, I could run ./program, type the script and still use stdin (in a scanf, for example). But I'd like to run ./program < script and still be able to use stdin (in a scanf).
My program is a simplified Pascal interpreter, that's why I need to run read(x) and write(x) in my scripts.
Yes, it's homework (the intepreter), but the doubt just popped up in the brainstorming process.
The current controlling terminal can be accessed using /dev/tty, even if stdin has been redirected.
ttyname(0) will return the filename of the current terminal associated with stdin. You can then open that and read from it.
If I understand what you're asking, you're asking for the ability to take in interactive input from a user when using file redirection, like the ./program < script bit above.
I don't believe there's a way to do that. A POSIX system will feed the script in via stdin and that's that. No interaction from the user.
It's also worth noting that you don't have to do anything special to realize that. Just treat stdin like you normally would. You don't have to think about whether it's coming in interactively or from a file, which is really quite nice.