I'm trying to run a C file using Notepadqq in Manjaro Gnome edition, but when I try running my script by going to the Run command it opt up a windows that says Special Placeholders
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This should be corrected fairly easily via the graphical user interface. No command or file modification should be necessary.
In Nautilus you can right click on the file to open.
I'm trying to run a C file using Notepadqq in Manjaro Gnome edition, but when I try running my script by going to the Run command it opt up a windows that says Special Placeholders enter image description here
To run a C program you need to compile it first, generate an executable and then run it as a normal system command. You cannot run it directly from Notepad++ because as such, it is not still executable. This is generally done with a program called a C compiler (which you don't mention if you have one or not) I figure that you are on a Windows computer, so the variety and availability of C compilers makes it impossible to continue giving you advice. You need to install a compiler, learn how to use it, and then you'll know how to make your C program executable in the system.
I recommend you to read a good programming book in C, like "The C Programming Language" from Brian Kernighan & Dennis Ritchie, to know how to compile a program and your operating system's manual to know how to execute a program.
Edit
Oh, sorry, you said on linux. You have to save your source file (with some name ended in .c) then compile it with something like
$ cc my_hello.c -Wall -o my_hello
where my_hello.c is the name you gave to the C source file, -Wall makes the compiler to be more verbose in explaining your C programming errors and -o my_hello specifies the compiler to output the executable command in a file called my_hello.
(I have represented the system prompt as $ and the screen cursor as _, you don't need to key those symbols) and then
$ my_hello
Hello$ _
(as you didn't end the line with \n, the next system prompt will appear next to your program's last message) to get it printed correctly, just modify your program to appear as
#include <stdio.h>
int main()
{
printf("Hello\n");
/* ^^-- insert the '\n' there */
}
Related
I am using a tool that has been written in C or C++.
https://github.com/kern-lab/discoal
I've never used C myself. In one of the files in discoal.h, I want to change: #define MAXSITES 220020 to #define MAXSITES 1100000. The tool manual says that I would have change the MAXSITES define in discoal.h and then recompile. How do I recompile?
I have never used C language before and I am not a Computer science student therefore, do not have much experience in programming either. Therefore, if you could let me know the command to recompile that'll be great. I've provided a link to that tool in case you want to look at the files.
Open a terminal, cd to the directory where the Makefile is, and type make, then hit Enter.
Prerequisites: A C compiler, which comes with Xcode on a Mac, as #Shawn commented.
I have a C program that needs to run when I turn on my machine (Red Pitaya).
the beginning of the program presented here:
//my_test program
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "redpitaya/rp.h"
int main(int argc, char **argv){
int jj=1;
while(1) {
printf("Ready for experiment number %i\n",jj);
int i, D;
int32_t TrigDly;
and so on...
the program is executable with a run.sh file called uri_test.sh, that contains the following:
cat /opt/redpitaya/fpga/fpga_0.94.bit>/dev/xdevcfg
LD_LIBRARY_PATH=/opt/redpitaya/lib ./my_test
both files are located in a directory under /root. the program is working perfectly when run manually on PuTTY terminal-
/RedPitaya/Examples/C/Uri# ./my_test
or
/RedPitaya/Examples/C/Uri# ./uri_test.sh
I tried to follow the solution presented here :
https://askubuntu.com/questions/9853/how-can-i-make-rc-local-run-on-startup
without success.
any suggestions? Thank you.
There are several ways to have a program running at startup, and it depends upon your init subsystem (are you using systemd or a SysV-style init?).
BTW, a source program in C is not a script and you generally compile it (using gcc -Wall -Wextra -g) into some executable. In your case, you probably want to set up its rpath at build time (in particular to avoid the LD_LIBRARY_PATH madness), perhaps by passing something like -Wl,-rpath,/opt/redpitaya/lib to your linking gcc command.
Perhaps a crontab(5) entry with #reboot could be enough.
Whatever way you are starting your program at startup time, it generally is the case that its stdin, stdout, stderr streams are redirected (e.g. to /dev/null, see null(4)) or not available. So it is likely that your printf output go nowhere. You might redirect stdout in your script, and I would recommend using syslog(3) in your C program, and logger(1) in your shell script (then look also into some *.log file under /var/log/). BTW, its environment is not the same as in some interactive shell (see environ(7)...), so your program is probably failing very early (perhaps at dynamic linking time, see ld-linux.so(8), since LD_LIBRARY_PATH might not be set to what you want it to be...).
You should consider handing program arguments in your C program (perhaps with getopt_long(3)) and might perhaps have some option (e.g. --daemonize) which would call daemon(3).
You certainly should read Advanced Linux Programming or something similar.
I recommend to first be able to successfully build then run some "hello-world" like program at startup which uses syslog(3). Later on, you could improve that program to make it work with your Red Pitaya thing.
As a beginner, I am trying to write a simple c program to learn and execute the "write" function.
I am trying to execute a simple c program simple_write.c
#include <unistd.h>
#include <stdlib.h>
int main()
{
if ((write(1, “Here is some data\n”, 18)) != 18)
write(2, “A write error has occurred on file descriptor 1\n”,46);
exit(0);
}
I also execute chmod +x simple_write.c
But when i execute ./simple_write.c, it gives me syntax error near unexpected token '('
Couldn't figure out why this happens ??
P.S: The expected output is:-
$ ./simple_write
Here is some data
$
You did
$ chmod +x simple_write.c
$ ./simple_write.c
when you should have done
$ cc simple_write.c -o simple_write
$ chmod +x simple_write # On second thought, you probably don’t need this.
$ ./simple_write
In words: compile the program to create an executable simple_write
(without .c) file, and then run that.
What you did was attempt to execute your C source code file
as a shell script.
Notes:
The simple_write file will be a binary file.
Do not look at it with tools meant for text files
(e.g., cat, less, or text editors such as gedit).
cc is the historical name for the C compiler.
If you get cc: not found (or something equivalent),
try the command again with gcc (GNU C compiler).
If that doesn’t work,
If you’re on a shared system (e.g., school or library),
ask a system administrator how to compile a C program.
If you’re on your personal computer (i.e., you’re the administrator),
you will need to install the compiler yourself (or get a friend to do it).
There’s lots of guidance written about this; just search for it.
When you get to writing more complicated programs,
you are going to want to use
make simple_write
which has the advantages of
being able to orchestrate a multi-step build,
which is typical for complex programs, and
it knows the standard ways of compiling programs on that system
(for example, it will probably “know” whether to use cc or gcc).
And, in fact, you should be able to use the above command now.
This may (or may not) simplify your life.
P.S. Now that this question is on Stack Overflow,
I’m allowed to talk about the programming aspect of it.
It looks to me like it should compile, but
The first write line has more parentheses than it needs.
if (write(1, "Here is some data\n", 18) != 18)
should work.
In the second write line,
I count the string as being 48 characters long, not 46.
By the way, do you know how to make the first write fail,
so the second one will execute? Try
./simple_write >&-
You cannot execute C source code in Linux (or other systems) directly.
C is a language that requires compilation to binary format.
You need to install C compiler (the actual procedure differs depending on your system), compile your program and only then you can execute it.
Currently it was interpreted by shell. The first two lines starting with # were ignored as comments. The third line caused a syntax error.
Ok,
I got what i was doing wrong.
These are the steps that I took to get my problem corrected:-
$ gedit simple_write.c
Write the code into this file and save it (with .c extension).
$ make simple_write
$ ./simple_write
And I got the desired output.
Thanks!!
Should a daemon on an embedded device using Busybox be written in C or as a script?
All the examples I have seen use #! /bin/ash at the top of the file and that is for scripting? But in the device I'm writing to has only complied C files (I think) and symbolic links in /usr/bin.
Every way I try to compile a C file with #include </bin/ash> (e.g. gcc -Wall -o daemon_busybox daemon_busybox.c) I get error after error report in /bin/ash:
/bin/ash:174:1: error: stray ‘\213’ in program
/bin/ash:174:1: error: stray ‘\10’ in program
/bin/ash:174:1: error: stray ‘\273’ in program
/bin/ash:174:1: error: stray ‘\204’ in program
/bin/ash:174:1: error: stray ‘\342’ in program
Note I have set this: /bin/ash -> busybox
Any ideas which way I should go?
Update:
I've been given the task trying to see if a daemon can be run on a small device that runs Linux (2.6.35-at-alpha4) and Java (SE Embedded Runtime Environment) with very limited memory (i.e. a 10 second wait to get java -version to report back).
Two weeks ago I didn't know much about daemons — only knew the word. So, this is all new to me.
On my development machine I have built two different daemon files, one in C and one as a script. Both run very nicely on my Linux machine.
But because of the very small size of the target device there is only busybox (no /lib/lsb/init-functions). So I'm trying to build a 3rd daemon file. I believe it should be written in C for this device, but all examples for busybox point to scripting.
Once your question is edited so that the file name you're trying to #include is visible, the problem becomes self-evident:
#include </bin/ash>
This tries to make the C compiler include the binary of busybox (via the symlink /bin/ash) into the code to be compiled. The average binary is not a valid C source file; this is doomed to failure.
Perhaps you simply need to drop that line — the C compiler stands a better chance of working if it is given header files and source files to compile. Maybe there's more work needed; we don't have enough information to help there.
Many daemons are written as C programs, but a carefully written shell script could be used instead.
Personally, I would like to do this as a script (I've never liked C). But on the device everything in the /usr/sbin folder looks like a C file. So, the conservative coder in me says C is the way to go. I know: ask the guys developed the device — but they're long gone. Right now my daemon is just a test (i.e. printf("Hello World\n"); ). I'm trying to get printf passed to Busybox. But so far I cannot get this file to compile. I just need a simple daemon in C to start.
OK; your C code for that should be just:
#include <stdio.h>
int main(void)
{
printf("Hello World\n");
return 0;
}
Save it in hw_daemon.c. Compile it using:
gcc -o hw_daemon hw_daemon.c
If that won't compile, then you've not got a workable C development environment for the target machine. If that will compile, you should be able to run it with:
./hw_daemon
and you should see the infamous 'Hello World' message appear.
If that does not work, then you can go with the script version instead, in a file hw_script.sh:
#!/bin/ash
printf "Hello World\n"
You should be able to run that with:
Predicted output — not output observed on a machine.
$ ash hw_script.sh
Hello World
$ chmod +x hw_script.sh
$ ./hw_script.sh
Hello World
$
If neither of those works at all, then you've got major problems on the system (maybe Busybox doesn't provide a printf command workalike, for example, and you need to use echo "Hello World" instead of the printf).
In my current example, I have a C file called 'Main.c' which converts and prints US pounds into UK stones/UK pounds/kilos, and the variable US pounds is currently defined by the user's input (scanf). The file itself is executed through Visual Express 2013; however, I want to change this so that I can navigate to the C file and execute the file directly through the commmand prompt (cmd) whiles passing a value to define US pounds.
I understand that this is required in main:
void main(int argc, char *argv[])
And I know how to navigate to the C file through the command prompt:
>cd Directory/To/The/File
However this is where I get stuck; I don't know how to execute the C file. I have researched into this and found several examples, such as using 'gcc' and 'cc', but the system doesn't recognise these commands. None of the materials that I have found fully explains what exactly I have to do in order to accomplish what I am trying to do; do I have to install something, or am I using the wrong commands, is it possible what I am trying to do, what excactly do I have to do?
Broadly speaking, you need to do the following:
Compile the program using a compiler to generate an executable.
Run the executable file.
When you "run the program in Visual Studio", it is doing all of those steps for you.
I don't know much about command line compiling in Windows, but I believe msbuild is the name of the compiler which Visual Studio uses. Look into that, and you'll see how to compile. Compilation will then generate the executable, which you just type into the command line to run.
EDIT: I found an article which suggests that cl is a C compiler command available on the command line.
Here is the relevant excerpt:
At the command prompt, specify the cl command together with the name of your source file—for example, cl simple.c—and press Enter to compile the program. The cl.exe compiler generates an .obj file that contains the compiled code, and then runs the linker to build an executable program that has the name of your source file, but has an .exe file name extension—for example, Simple.exe.
You cannot cd to the file, only to the directory. The cd command means "change directory".
You cannot execute a C file, it's just a text file and your computer doesn't know how to run it. You need to compile it first (this is what Visual Studio does). There should be an EXE file somewhere close, you need to find it. It is the binary, executable, form of your C program which you can run directly from the command line.