Debian Programming :: Assign Variable In Bash When Stdout Is Updated
Jan 17, 2014
I am writing a script that calls a program which writes a lot of lines to stdout continuosly. If the last line in stdout has some regex, THEN, certain variables are updated. My problem is that I don't know how to do that.
A simplified example would be (it's not my exact case, but it I write it here to clarify): suppose I issue a ping command (which writes output to stdout continuously). Every time that the response time is t=0.025 ms, THEN, VARIABLE1=(column1 of that line) and VARIABLE2=(column2 of that line).
I think the following code would work in awk (however, I want the variables in bash and I don't know how to export them)
In the previous code, awk analyzes each line of the output of the ping command as soon as it is created, so the variables $var1, $var2, ... are updated at the appropriate time. But I need the "real-time" updated values of $var1, $var2 in bash, for later use in the script.
At my wit's end I can't find anything that I understand well enough to use. This is for a Unix class, we are working with shell scripting. File1 has 5 in it and File2 has 100 in it.The teacher wants us to read the values then do the math. This is what I have so far:#!/bin/bashvar1='cat File1'var2='cat File2'var3=`echo "scale=4; $var1 / $var2" | bc`echo The final result is: $var3
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).
I'm writing a script to execute bash commands in the PHP CLI. I would like to suppress errors from bash and write my own error message if an error occurs. So far I have this (assuming log.txt doesn't exist!):
Code:
tac log.txt 2>/dev/null
Which works as expected, tac kicks up an error but the error is suppressed, but when I use this:
Code:
tac < log.txt 2>/dev/null
I get:
Code:
bash: log.txt: No such file or directory
The tac error is suppressed but bash still gives me a dirty error.
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.
Instead of a steady output of lines to the terminal, output only occurs after a few seconds, between 6 or 12. This happens whether the input is from mplayer or avconv/ffmpeg. This never used to happen (a few years ago) so I wondered whether an awk update caused this to happen.
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 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'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".
