Programming :: How To Use Bash Variable In C Code?
Feb 16, 2011
I want to write a c program with some shell scripts.Now For a simple C program. I am Setting a variable called val2 in bash, now I want to use bash variable val2 in C code. How do I do that?The above doesn't work (coz its spawning a different memory space and when shell script ends the variable dies with it as per my research but how do I keep them in same memory space)Also Is there any Good reference where they teach how to integrate C and Bash Together?
I'm trying to read content of file to variable and use this variable in for loop. The problem is, when I have c++ comment style in file - /*. Spaces in line are also interpreted as separated lines.
For example:
Code:
Changing $files to "$files" eliminate these problems but causes that whole content of variable is treated as one string (one execution of loop).
Now in my bash script, I want to get the output /home/user instead of $HOME once read. So far, I have managed to get the $HOME variable but I can't get it to echo the variable. All I get is the output $HOME.
I'm writing a tridiagonal solver for sparse linear systems and I coded this decreasing loop:
PHP Code:
xx[NN - 1] = gamma[NN - 1]*BB[NN - 1]; ii = NN - 2; /* Compute the x values: */ while (ii >= 0) { xx[ii] = gamma[ii]*(BB[ii] + xx[ii + 1]); ii = ii - 1; }
now... if ii is declared as an unsigned integer, the code gives me a segmentation fault, but if I declare it as an int, it doesn't. Using DDD I noticed that, as an unsigned int variable, when I finally decrease it, it underflows and blows up to a huge value, ergo giving me an unaccesible direction for xx in the following iteration! I taugh me not to use unsigned int variables for dereasing loops! XD
Just a simple BASH for loop to read the file path from a text file (clean.txt) echo the variable for debug purposes, and scp it to a server I have using port 50 for SSH.
I've already formatted the entries in clean.txt to handle spaces correctly, using sed replacement.
Example from the clean.txt file:
Code: /MP3/NAS000000001/Barenaked Ladies/Barenaked Ladies - Barenaked For The Holidays/20 Auld Lang Syne.mp3 /MP3/NAS000000001/Barenaked Ladies/Barenaked Ladies - Barenaked For The Holidays/14 Deck the Stills.mp3
i've just started to learn about functions in Bash scripting. I'm able to set the functions and execute the commands correctly. However, if my_var is set in the first function and then later in the script in the script the 2nd function is called, it doesn't seem to remember my_var and quits (at least i suspect this is the problem).
Here's my code (it requires yad available via webupd8. org). My specific problem seems to lay in line #27 where if we view the changelog and then exit that window, it returns to the "main" function but any subsequent commands cause a crash. Is this because of the get command on line #29? It's presumably now out of scope after calling menu on line #25?
I have a file with around 1000 IP addresses in it and I need to be able to ssh into each one of them, run a single command, and then exit. I already know the ssh command I want to run and it looks like this:
(I know shpass is not good to use and keys are the correct way but I don't have any other options in this scenario.) if these ip addresses were in a .csv file, by themselves with no other information, how would I create a script to do the above command to each ip until the end of the file?
An input filename ($1) is fed into mediainfo, which by the use of grep and cut spits out a single number which is the aspect ratio. This is then divided by bc into 320, which gives the desired height dimension for the file that I want ffmpeg to create for me. Finally, ffmpeg runs using the calculated dimensions... Basically, it's the passing of the $ASPECT variable to bc that seems to fail. It looks like bc won't read the output from the mediainfo line... It always crashes out with:
Code:
(standard_in) 1: illegal character: ^M I've tried doing something even simpler like this to debug by just trying it to display the calculation on the screen:
I have a program that loops over each word in a sentence. I need to append a constant to the beginning and end of each word. It works up until the last word on the line.
I was wondering if possible in bash for a variable to take the value of a function, I mean the function returns a value and a variable will take it. example:
The output of following code is not like it's intended ...
Code:
This is the output:
Code:
Test prepending ...apple is a nice word, hour is a nice word, But of course what I want to do in the first set of commands is to prepend the word "an" to the words "apple" and "hour" in the for-loop.
Within a bash script, I'm attempting to redirect file descriptors with exec, e.g. exec 3>&1 1>&2; however, I'd like to do something like exec $FD>&1 1>&2, which doesn't work because bash tries to execute the value of $FD. Various placements of eval fail, as well. Is there a way around this, or am I stuck hard-coding the descriptor?
So that when I grep on the local file again later, it can be printed out with original log lines. Otherwise, the log lines will be dropped and lines becomes concatenated into a single line, e.g., if I rewrite the script in this way, echoing the $result is not a good idea..
is there some workaround that I can save it to a variable rather than file but still keep the eol? That will simplify my script and don't need to do all those I/Os!
I have a bash script that calls a java class method. The method returns a string to the linux console when run independently. how can I assign the value from the java method to a variable in a bash script?running the script: java -cp /opt/my_dir/class.method [parameter]
Is there a variable which will tell you which keyboard mapping you are using? I want to write a bash script that will change my keymapping from Dvorak keyboard to US keyboard. I cannot seem to find a variable to read from. I was going to use the "if [ ] then; statement".
2. for I in 1 2 3 4 5 6 7 8 9 10; do echo $I; done|
3. for I in $(seq 1 10); do echo $I; done|
4. for ((I=1; I <= 10 ; I++)); do echo $I; done
I have a script which uses the 1st form of for loop. I'm trying to modify it to use a variable instead of a static hard-coded value in the section that controls the looping.of the for loop.
I've tried all different ways of quoting and escaping the variable, and the problem is that the quoting chars and escape char are being translated and passed into the loop along with the value stored in the variable.
For example, to change the start value of 1 to whatever value I want passed in through a variable:
Change:
I have tried: {{$a}..10} and {`$a`..10}, to have the variable evaluated first.
I have tried using the eval() function.
I have tried single and double quotes and the backslash escape character.
Nothing I've tried works. It's probably a syntax error.
I'm setting up a machine that's going to be used to test randomly connected tape drives one at a time, and as such, I'm writing the test routine using mt in a bash script, for user-friendliness. The problem is the block device name changes on occasion as tape drives are swapped out and busses are rescanned, so I can't "hard code" a block name into the script.
I know programs like lsscsi and hwinfo will give you block device names as part of their output, but I can't seem to grep anything in such a way as to have the final output be just the block name (ie /dev/st2, or optimally 'st2'), so that I can just have the script read said output, and drop it into the necessary variable.
I am having all sorts of trouble trying to assign a variable within an awk script with the system command. I know there is a lot of ways around this problem, but for efficiency reasons, I would like to, within my awk script, do something like
system(x=3)
or
system(x=NR)
and, latter on the shell script which calls the awk script, use the variable $x. But nothing is passed to x. I have already tried things like
command = "x=3" system(command)
and also used a pipeline within the system to pipe it to /bin/sh In fact tried a lot of stuff like that, using $(( )) etc etc etc I can create directories e write to files (yes, i could write to a file and read from there, but I dont think it is efficient, plus I am puzzled).
I am fairly new to bash scripting, and I am trying to test a variable against a number range (1-3). This is what I have used so far: The user enters a value, then
I think read A1 A2 makes A1, A2 string variables. Then, when A2 gets the value 01, '01' should be a string. But for some reason bash takes it as numeric. I know there are no types in bash.
I'm trying to implement an assert function similar to:[url]
However, I'm having trouble with file existence testing when the file name has a space in it.
I have distilled the problem down to the following:
This code works as expected, printing 'yes' if '~/test file' exists, and no if not.
Code:
However, this code gives an error.
Code:
The error:
Code:
Which tells me that it is splitting ["~/test file"] into ["~/test] and [file"]. Why? Is there a way around this?
Note that if you simply use a file path without a space, both cases work perfectly. Is this a BASH bug possibly? I just can't understand why the first would work, but the second wouldn't.
I have been scripting (or programming) in Bash shell for around 2+ years now. I have heard that ksh and zsh are better shells than bash. Are there any differences on the scripting side too, I mean is it easier to write a script in ksh or zsh rather than bash? Is there any benefit to code in ksh or zsh instead of bash.
