All Questions
74 questions
1
vote
1
answer
395
views
Why pipes not working for cat | cat | ls?
I really need help and any suggestions will be very welcomed. Me and a mate have coded a mini version of the Shell and I did parsing and executing parts. All is working properly except for some cases ...
- 15
0
votes
1
answer
56
views
bash cat pipe supposedly misbehaving
In the following, I have made echo to write to stderr; then it's piped to cat, which has both output streams connected to /dev/null.
$ echo something 1>&2 | cat 2>&1 >/dev/null
...
- 149
1
vote
1
answer
152
views
An error occurred while processing STDERR using the pipe
My working directory is as follows:
MyWorkDirectory
└── test
The file "test" contains a line of information：
1:2:3:4:5
When I use the following command:
cat test foo
the output is as ...
- 13
0
votes
2
answers
34
views
Unix concatenation commands
I've got a question here that I dont understand:
cat abc.dat | tee bcd.dat | tr ab ba > cde.dat
In this instance, I understand the translate part, but I’m a little confused as to what the pipe | ...
- 61
0
votes
1
answer
45
views
Why does a *.sh script executed on a remote machine sometimes return only partial output?
I run a command cat getStorage.sh | ssh -T remoteHost >> storageLog.csv.
getStorage.sh looks like this:
#! /bin/bash
dateTime=$(date)
echo -n $dateTime,
df -h /directory/ | tail -n 1 | awk '{ ...
- 263
0
votes
2
answers
1k
views
How to slow down the cat command without piping the output to the more command? [closed]
Bash version 4.4.0
Ubuntu 18.04.5 LTS
Is there a way to slow down the cat command to a crawl so I can visually see the output of a file without piping the output into the more command or another file?
- 1,048
0
votes
1
answer
554
views
Reading data from standard input using two threads
I am trying to read data from standard input (stdin) using two threads but I'm not able to read data properly. I tried on Linux platform using gcc compiler. I am trying to read data using cat command ...
- 34.5k
0
votes
0
answers
382
views
Use pipes to change the input entered using cat command in child process in C
I have an operating systems problem where I need to execute the 'cat' command in the child process. The child process is created using fork() system call. While running 'cat' command in the terminal, ...
5
votes
3
answers
4k
views
how to pipe ls into cat with xargs so that filenames are listed?
For using cat to output *.txt files within a specific directory, how can I insert the filename as a "break" before each file?
file #1
contents of file
file #2
contents of file
ideally as ...
- 8,476
0
votes
1
answer
969
views
tcsh passing a variable inside a shell script
I've defined a variable inside a shell script and I want to use it. For some reason, I cannot pass it into to command line that I need it in.
Here's my script which fails at the last lines
#! /usr//...
- 1,131
0
votes
1
answer
766
views
Create a file with the content of 2 other files, then sort the new file
I am using the following command: cat < file1.txt | tee >> unsorted.txt | cat < file2.txt >> unsorted.txt | sort -r unsorted.txt > sorted.txt
If i run this line once i get an ...
0
votes
1
answer
633
views
How to find file and print the content of the file by using find and cat (is it possible?)
so I am fairly new at working with Linux and i was wondering if there is any way to use find commando to find a file in a location then pipeline it to print out (with cat commando) the content of that ...
- 1
-1
votes
1
answer
274
views
Linux print file and use it in for example a curl request
This might be a complete noob question, but I would like to know a simple oneliner to solve my problem.
Imagine following: I have 5 files, could be .txt, .sql .anything.
root@DESKTOP:/$ ls
test.sql ...
- 142
2
votes
1
answer
387
views
Can I make a shell function in as a pipeline conditionally "disappear", without using cat?
I have a bash script that produces some text from a pipe of commands. Based on a command line option I want to do some validation on the output. For a contrived example...
CHECK_OUTPUT=$1
...
...
- 17.2k
0
votes
1
answer
231
views
create a file using Cat in terminal and pass the file to another command
I have CLI command which works great when the file is created somewhere outside and the filename input is given to the command.
For eg:
mycli create rr --filename ./example/rule.yaml (works perfectly)
...
- 729
0
votes
1
answer
892
views
How to use grep with curl for lots of urls and return $url
After a lot of cutting and filtering i got a list of urls, in a text file.. i want to pass these urls to a curl command to curl all the urls in the text file and at the same time, grep the output of ...
0
votes
1
answer
261
views
Executing cat|grep|grep using 2 pipes
Title is self-explanatory on what I want to do so here is my current code:
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
int main() {
...
- 275
0
votes
3
answers
1k
views
Piping into grep using cat returns error: no such file or directory
I am practicing on bash. When I try this command, I get an error: "grep: where: No such file or directory".
cat file2.txt | tr " " "\n" | grep –i where | wc -l
Content of file2.txt = 1 2 3 4 where 5 ...
- 75
1
vote
0
answers
37
views
Debugging fails when reading input from file [duplicate]
pdb exits with a BdbQuit exception when I try to use it within my script main.py which is run as follows:
cat input_file.txt | python main.py
You can reproduce the error using the following example:
...
- 21
3
votes
1
answer
8k
views
Pipe Command Output into Awk
I want to pipe the output of a command into awk. I want to add that number to every row of a new column in an existing .txt file. The new column should be at the end, and won't necessarily be column ...
- 571
1
vote
2
answers
57
views
Command to replace string in one file with content of another file
The file /var/cpanel/mainip contains the main IP of my server and nothing else.
The file /etc/csf/csf.blocklists contains a list of firewall blocklists, and part of the file contains a line with an ...
- 23
0
votes
3
answers
319
views
Overriding file in bash in one pipe
The result of cat file1 | cat > file1 is empty file1.
The result of head file1 | cat > file1 is empty file1 as well.
Of course, a real pipe is intended to have more steps - tools and ...
- 8,339
2
votes
2
answers
3k
views
Pipe cat/grep/arguments into variable in bash script
#!/bin/bash
DATE=`date +%Y-%m-%d`
HOUR=`date +%H`
ORDERS_THIS_HOUR=`cat cli.log | grep $DATE $HOUR | grep -o "generated for Production" | wc -l`
OUTPUT="$DATE $HOUR : $ORDERS_THIS_HOUR"
echo "$OUTPUT"...
- 756
5
votes
2
answers
11k
views
Pipe multiple verbatim lines into command in bash
I am trying this in GNU bash, version 4.4.12(1)-release (x86_64-pc-linux-gnu):
$ echo <<EOF | cat
> 1
> 2
> 3
> EOF
I would have expected three lines of output (with 1, 2, 3), but ...
- 2,579
0
votes
1
answer
908
views
Piping multiple commands to bash, pipe behavior question
I have this command sequence that I'm having trouble understanding:
[me@mine ~]$ (echo 'test'; cat) | bash
echo $?
1
echo 'this is the new shell'
this is the new shell
exit
[me@mine ~]$
As far as ...
user3566909
-1
votes
1
answer
47
views
Get current line of a file that is piped to a command
My goal is to figure out a PIN password for a daemon listening at port 30002.
So I created a dictionary called pinlist and i pipe it to nc (netcat) localhost 30002
This is the command:
cat pinlist | ...
- 113
1
vote
0
answers
1k
views
java Runtime.getRuntime().exec using cat and piping
I'm trying to run the following command through java to show the current wifi signal strenght :
cat /proc/net/wireless | awk 'END { print $4 }' | sed 's/\.$//'
In the terminal this command works ...
- 75
0
votes
2
answers
263
views
Makefile on windows: unable to locate cmd.exe directory
I am facing an issue when I try to run a Makefile on windows (working with Cygwin).
I have this line of code:
cat command.bat | "$(cmddir)"
cmddir was defined as cmddir := /C/Windows/System32/...
- 75
4
votes
0
answers
896
views
Gradle 'exit' in a shell script [duplicate]
I want to build a package by Gradle (3.2.1) using a script.
The script (hoge.sh) is
#!/bin/sh
gradle build
echo "hello"
./hoge.sh works and prints "hello".
However, cat hoge.sh | /bin/sh -s stops ...
- 995
1
vote
1
answer
1k
views
Hadoop hdfs cat pipe edgenode to hdfs
I am trying to send data from the local edgenode to hdfs as a pipe. The purpose is to simulate data coming from an external server going through the edge node hitting a pipe and then landing it in ...
- 817
2
votes
2
answers
1k
views
cat multiple files and subshell
Is there a single shell command that will do the following:
cp header page.html
markdown page.md >> page.html
cat footer >> page.html
(Markdown outputs to stdout by default.)
A ...
user1569030
0
votes
2
answers
160
views
How would I go about creating a flow chart representing a linux grep command?
I am currently using the Linux terminal and command:
cat [filename] | grep [searchword]
To search a file contents for a specific word/string, but how would i represent this command within a flow ...
0
votes
1
answer
4k
views
The use of pipping and wc -w in UNIX
I had a midterm exam and one of the questions were:
what does the following command do step by step:
cat file1.txt | wc | wc -w > file2
Then What would be displayed on the standard out of "cat file2"...
- 13
1
vote
1
answer
456
views
How to pipe virtual files?
I am using these commands to convert some files in inkscape:
python dxf_input.py sample.dxf > output_ink.svg
python scour.inkscape.py output_ink.svg > output.svg
This method works prefectly ...
- 2,913
3
votes
0
answers
1k
views
How does pipe behave in a cron job script?
I have some data in some files and I am piping the data to a filter using cat.
cat /home/user/data1.bin /home/user/data2.bin |
/home/user/bin/datafilter -f /home/user/output.txt
When I run ...
- 1,278
-2
votes
3
answers
1k
views
Why is `ls hello.txt | cat` different from `cat hello.txt`? [closed]
I wonder why ls hello.txt|cat does not do the same thing as cat
hello.txt? I am trying to pass the result of ls to cat, which seems to make sense, because the result of 'ls hello.txt' is hello.txt ...
- 10.2k
0
votes
1
answer
841
views
Linux: cat to named pipe in a python script
I have a Java program that uses video from a framegrabber card. This program is launched through a python launcher.py.
The easiest way to read the video stream I found, is to make Java read on a ...
- 1,892
1
vote
2
answers
117
views
C++: Linux code does not work on Windows - piping data to program
I'm looking for some help piping a file (16-bit signed little endian integers raw data) from the command line to my program:
cat rawdata.dat | myprogram
The code works pretty well on Linux, 512 ...
- 85
0
votes
3
answers
2k
views
Piping filename from standard input in linux into c++
I want to be able to write a line in a terminal (as below) that takes a text file in the same directory and inputs its name into an executable file.
cat fileName | executable
I want to be able to ...
- 33
6
votes
2
answers
4k
views
Piping a data file with cat to a C++ program
I'm looking for some help piping a file (16-bit signed little endian integers raw data) from the command line to my program:
cat data.dat | myprogram
Then it should convert the data to 16 bit signed ...
- 85
1
vote
2
answers
1k
views
Pipe Operator in Linux
As per my understanding, the pipe operator in Linux takes standard output of the one command and channelizes it to the standard input of the next command. But I have faced one anomaly.
I am trying to ...
- 11
-2
votes
3
answers
87
views
New to using Linux
Using a pipe, sort a directory listing (i.e. list contents of directory and sort)… then pipe this output into cat and redirect the output into a file named “exercise5.7.txt”. I sorted the list ...
4
votes
1
answer
335
views
Why is piping into cat faster than not piping to cat?
I've just found out that doing find . is slower than doing find . | cat. Here's the results of doing time find . 3 times in my home directory:
First:
real 0m4.385s
user 0m0.546s
sys 0m2....
- 534
0
votes
1
answer
2k
views
Command line tool to get binary data as String in Windows like Cat?
So I have program that transforms data by piping the string into stdin like so.
cat input.mp3 | myexe
except I want this commandline tool to run on Windows.
type input.mp3 | myexe.exe
and cat and ...
- 2,752
3
votes
1
answer
3k
views
Unix piping - echo and cat
I am having trouble with the following command in Unix Bash Shell:
echo "This is some text" | cat dashes - dashes
"dashes" is a file containing the line of text:
"---------------------------------"
...
- 648
0
votes
2
answers
35
views
Trying to collect output from multiple statments
Is there a way to wrap all of this write (pun intended) no only ``` is in temp.md
echo "\`\`\`" && cat temp.txt && echo "\`\`\`" > temp.md
- 59.2k
0
votes
2
answers
133
views
How do I cat a file piped from echo?
I would expect this to print the contents of foobar.txt:
echo "~/sandbox/foobar.txt" | cat
But instead it just prints to the console:
~/sandbox/foobar.txt
How can I cat the file contents instead ...
- 3,323
2
votes
1
answer
97
views
Difference in `< <(cat file)` and `<file` feeding loop
I saw the following example for reading a file in a bash script:
while read IP; do
${IPTABLES} -I INPUT -s "${IP}" -j DROP
done < <(cat "${BLACKLIST}")
but I'd have thought to do the ...
- 1,435
0
votes
1
answer
1k
views
How to use a mixture of cats and pipes in subprocess
I am trying to cat the contents of a file and pipe it into the stdin of a second python script, then put the stdout of that into another file.
On the command line it looks something like this:
cat ...
- 995
0
votes
2
answers
59
views
how to append the text from daughter files to a single mother file and deleting headers from daughter files
During a structural simulation, I get the following response in a file.txt:
constant
date 03/23/2011
{BEGIN LEGEND}
Entity # Title
1 ...
- 31