1
vote
1answer
43 views

Understanding grep and pipes in linux

I came across this post which explains my problem. Suppose there is a file called file.txt which contains "foo World". The answer posted by Tyler explains a lot however I am confused as to how cat ...
3
votes
1answer
30 views

Can close() block?

For example, if you close a pipe or socket that still has data in its write buffer that hasn't been read by the process on the other end, does close() block until the data is read or the other process ...
14
votes
2answers
1k views

How do I “cat and follow” a file?

A file is being sequentially downloaded by wget. If I start unpacking it with cat myfile.tar.bz2 | tar -xj, it may unpack correctly or fail with "Unexpected EOF", depending on what is faster. How to ...
3
votes
2answers
631 views

grep string from contents of file command then delete file

I have a peculiar problem I need help with. I have a large batch of .docx files where a certain number of them are junk. I know how to identify these files from the file command, as they contain the ...
4
votes
3answers
473 views

How to capture stdout of a running process redirected to /dev/null

I want to capture stdout of running process whose stdout is being redirected to /dev/null. I tried using system call fcntl(), however the moment I close fd "1", it was being allocated for other files ...
0
votes
2answers
522 views

Redirecting stdin with stdout to file

So I have a program that takes in user input and outputs text based on the input. EDIT2: I want to create a script that runs a C executable and the script feeds the C program input from a file and ...
3
votes
4answers
4k views

Piping output to text file within a for loop

I'm trying to do the following within a for loop: Find files that satisfy a condition Echo the name of the files to a log file. Gzip the file. I can get the script to find the files and echo their ...
10
votes
2answers
4k views

Pseudo files for temporary data

I often want to feed relatively short string data (could be several lines though) to commandline programs which accept only input from files (e.g. wdiff) in a repeated fashion. Sure I can create one ...
3
votes
1answer
52 views

Emulating a file

I have certain application that opens a file with given path (presumably with fopen or derivative), reads the file, possibly writes to it and closes it. I have no control over this application other ...
3
votes
3answers
106 views

How to include program which only works with in/out files into a pipeline?

I need to process image with several tools in a pipeline tool1 | tool2 | tool3 | .... It appeared though that one of the tools isn't designed to work in a pipeline and only works in format of ...
1
vote
1answer
192 views

Magic file that redirects to standard output

Is there a magic file name that gives the following effect? $ mkfifo /tmp/fifo1 && cat /tmp/fifo1 & $ foo --log-file /tmp/fifo # now I can see the log as the program runs I want ...
4
votes
0answers
159 views

Repeatably generate a read error for testing? [duplicate]

I'm trying to test the error handling in some software, in particular what happens when an error occurs reading from a file or pipe. Is there a simple way to send a certain amount of data to stdout ...