I am having difficulty figuring out how to implement grep into my CGI script. Basically I will receive a value of eg. 1500 from a HTML page. The CGI script then runs and compares 1500 to a text file. When it finds 1500 it prints the entire line and displays it on the webpage. I would like some tips and pointers on how to do this please. I understand that this involves grep but I don't really know how to put it in.
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char *data;
long m,n;
printf("%s%c%c\n",
"Content-Type:text/html;charset=iso-8859-1",13,10);
printf("<TITLE>Webpage of Results</TITLE>\n");
printf("<H1>Temperatures</H1>\n");
data = getenv("QUERY_STRING");
The HTML passes the variable time=1500. I understand (correct me if I am wrong) that QUERY_STRING will contain 1500?
some very straightforward analog of the grep in C is strstr() function
For a URL of the form whatever?query-string, the enviroment variable QUERY_STRING contains the full query-string - in you case time=1500 or similar.
You need to remember that there may be more then one field/value getting passed, seperated by &. By using strtok() you can retrieve the parts of the query string one by one, strcmp() lets you compare them to other strings.
If you found the right token, you need to work with a file:
fopen() is used for opening a file
fgets() is used to retrieve a line
use strstr() to check if a line contains a certain substring
use fclose() to close the file when you're done
Related
I'm writing a reusable function, so I need the argument to be as flexible as possible.
Consider a simple example:
function testf(){
print ./*.$1
}
This works. For example, with testf mp3 it lists all the files ending with .mp3 in an array, making possible the use of for loops. But this way it only allows me to work with the extension name.
Therefore, I tried:
function testf(){
print ./$1
}
However, it doesn't work. Using testf *.mp3, unlike using print *.mp3 in the terminal, it will only pass the first matching string instead of the whole array.
Any suggestion?
ists all the files ending with .mp3 in an array ... there is no array involved in your question.
But to your problem: First, you want to pass to your function a wildcard pattern, but this is not what you are actually doing. testf *.mp3 expands the pattern before the function is invoked (this process is called filename generation), and your testf gets just a list of files as parameters. You can pass a pattern, but you have to ask the shell not to expand it:
testf '*.mp3'
In this case, your $1 indeed will contain the string *.mp3. However, your print ./$1 will still not work. The reason is that filename generation occurs before parameter expansion (which is the process where $1 is replaced by the string it contains). Again, you have to ask the shell to do it the other way round:
print ./${~1}
The shell performs several types of expansions before launching the command. When you enter
testf *.mp3
the shell will expand the glob first, and pass each filename as a separate argument to the function
Your function could look like this:
function testf(){
printf './%s\n' "$#"
}
I am trying to use a formatted string to identify the file location when using 'print -dpdf file_name' to write a plot (or figure) to a file.
I've tried:
k=1;
file_name = sprintf("\'/home/user/directory to use/file%3.3i.pdf\'",k);
print -dpdf file_name;
but that only gets me a figure written to ~/file_name.pdf which is not what I want. I've tried several other approaches but I cannot find an approach that causes the the third term (file_name, in this example) to be evaluated. I have not found any other printing function that will allow me to perform a formatted write (the '-dpdf' option) of a plot (or figure) to a file.
I need the single quotes because the path name to the location where I want to write the file contains spaces. (I'm working on a Linux box running Fedora 24 updated daily.)
If I compute the file name using the line above, then cut and paste it into the print statement, everything works exactly as I wish it to. I've tried using
k=1;
file_name = sprintf("\'/home/user/directory to use/file%3.3i.pdf\'",k);
print ("-dpdf", '/home/user/directory to use/file001.pdf');
But simply switching to a different form of print statement doesn't solve the problem,although now I get an error message:
GPL Ghostscript 9.16: **** Could not open the file '/home/user/directory to use/file001.pdf' .
**** Unable to open the initial device, quitting.
warning: broken pipe
if you use foo a b this is the same as foo ("a", "b"). In your case you called print ("-dpdf", "file_name")
k = 1;
file_name = sprintf ("/home/user/directory to use/file%3.3i.pdf", k);
print ("-dpdf", file_name);
Observe:
>> k=1;
>> file_name = sprintf ('/home/tasos/Desktop/a folder with spaces in it/this is file number %3.3i.pdf', k)
file_name = /home/tasos/Desktop/a folder with spaces in it/this is file number 001.pdf
>> plot (1 : 10);
>> print (gcf, file_name, '-dpdf')
Tadaaa!
So yeah, no single quotes needed. The reason single quotes work when you're "typing it by hand" is because you're literally creating the string on the spot with the single quotes.
Having said that, it's generally a good idea when generating absolute paths to use the fullfile command instead. Have a look at it.
Tasos Papastylianou #TasosPapastylianou provided great help. My problem is now solved.
How would you stick a string of hexcode into a .bin file? Like this, \x45\x67\x89 for example. I've seen the long examples where you use bash to strip it then add it to the .bin, but there must be a quicker and simpler way?
Also, I am not too familiar with .bin's, are they a program in themselves?
printf is function wide supported function. C, cpp, php, python, bash...
so classic implementation in C would be:
FILE *fp =fopen('binfilename.bin', 'w');
fprintf(fp, "\x45\x67\x89"); fclose(fp);
all other languages have similar usage.
you mention bash, and i think there is no simpler way than bash itself:
printf "\x45\x67\x89" > binfilename.bin
Every file is binary file. If it contains just printable bytes, we call it textual file. If it is generated by compiler and have bytes meaningfull to cpu, not to human, than we say it is 'binary', program. But both textual and binary contains bytes and are binaries. Difference is after, when we/some app interprets it's contents.
I am in the process of writing an HTTP client that basically goes to a webpage and downloads the content to a separate file, which the user defines. I am having trouble not with the act of writing to a file itself, but I'm getting a strange problem. I'll show a couple of the code snippets below, but basically when there is a
fprintf(stdout, "%s", htmlcontent);
where htmlcontent is defined as
char *htmlcontent;
it prints out the entire HTML page information to the standard output. I can also redirect this output to a file in the command line by saying >myfile.txt (Yes, I want to compare the text files instead of html files).
But when I do something like this:
fprintf(savedfile, "%s", htmlcontent);
where savedfile is defined as
FILE *savedfile;
and it is opened like this:
savedfile = fopen(filename, "w");
where filename is defined as
char *filename;
and is set equal to the command line argument that corresponds to it. When I do the second type of fprintf to print it out to my file instead of the standard output, I do not get the same thing and i can't figure out why. Can anybody help me understand why there would be any difference? If you want me to post the two different programs so you can see them in their entirety just let me know and I'll do that.
You haven't really told us what the difference is between the two output methods but, based on the information given, there should be none.
Functionally, there's no difference between writing to stdout and any other properly opened output stream (there are some behavioural differences like buffering but they shouldn't affect the output).
The following transcript shows this in action:
pax> cat xyzzy.c
#include <stdio.h>
int main (void) {
char *filename = "xyzzy.txt";
char *html = "<tag>some markup</tag>\n";
FILE *xyzzy = fopen (filename, "w"); // should error check
fprintf (stdout, "%s", html);
fprintf (xyzzy, "%s", html);
fclose (xyzzy);
return 0;
}
pax> ./xyzzy
<tag>some markup</tag>
pax> cat xyzzy.txt
<tag>some markup</tag>
As you can see, both the xyzzy.txt file and the standard output of the program contain the same information.
>> set signal_name [get_fanout abc_signal]
{xyz_blah_blah}
>> echo $signal_name
#142
>> set signal_name [get_fanout abc_signal]
{xyz_blah_blah}
>> echo $signal_name
#144
>>
I tried other stuff like catch etc, and every where, it returns #number. My goal is to be able to print the actual value instead of the number - xyz_blah_blah.
I am new to tcl. Want to understand, if this is an array or a pointer to an array or something like that. When I try the exact same thing with a different command, which returns just a value, then it works. This is a new command which returns value in parenthesis.
Please help. Thanks.
Every Tcl command produces a result value, which you capture and use by putting the call of the command in [square brackets] and putting the whole lot as part of an argument to another command. Thus, in:
set signal_name [get_fanout abc_signal]
the result of the call to get_fanout is used as the second argument to set. I suggest that you might also like to try doing this:
puts "-->[get_fanout abc_signal]<--"
It's just the same, except this time we're concatenating it with some other small string bits and printing the whole lot out. (In case you're wondering, the result of puts itself is always the empty string if there isn't an error, and set returns the contents of the variable.)
If that is still printing the wrong value (as well as the right one beforehand, without arrow marks around it) the real issue may well be that get_fanout is not doing what you expect. While it is possible to capture the standard output of a command, doing so is a considerably more advanced technique; it is probably better to consider whether there is an alternate mechanism to achieve what you want. (The get_fanout command is not a standard part of the Tcl language library or any very common add-on library like Tk or the Tcllib collection, so we can only guess at its behavior.)