io redirection is the process of changing where the output and input of a program originate

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Throw away standard output and error

I have redircted my ouput using /dev/null in bash script but it is still throwing an error. Code is following ps -p $proc | fgrep $proc> /dev/null if [ $? -ne '0' ] ; then ...... fi below is ...
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4answers
251 views

grep command not working in conditional statement

I've a bash script that's supposed to go over all the filenames and print them only those that contain a certain letter (let's say it's 'o'). What I've done: command=`ls -l` for file in $command do ...
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0answers
27 views

Inherit IO redirections from a script to another

When I redirect the output of a script within a script, I expect the redirection to be applied to the called script as well as the program called within it. A: ./B 2>> error.log B: ...
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1answer
38 views

need to get the command information over ssh and the input from file

I am writing a script to get the command information of the remote machine usinf while and for loop. PFB the script. But the script ends by giving the single command information only. I have multiple ...
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42 views

How to rewrite the comand using I/O redirections?

Is there any way to rewrite the following command using only I/O redirections and not pipes ? ls -l | grep User | wc -l | tail -l
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1answer
20 views

A generic cron wrapper that records all output

I am hoping to write a cron wrapper that records all output in a folder $CRON_LOG_DIR. It would be used as, e.g., follows: * * * * * $CRON_WRAPPER "<job name>" "command" which would record ...
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1answer
87 views

Problem with paste and standard output in linux

I have two files that I am trying to merge, one file is: linux$ cat temp2 linear_0_A_B linear_0_B_A 103027.244444 102714.177778 103464.311111 102876.266667 103687.422222 103072.711111 103533.244444 ...
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1answer
44 views

Write permissions inside of shell script

I am using a Debian 7 Server. I created a shell script to be executed by crontab to save a mysqldump every day. mysqldump *database* -u *mysql-user* -p*mysql-password* > ...
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1answer
44 views

How to create dynamic process substitution based on the input (multiple FIFOs)?

I'm trying to create multiple process substitutions based on the output from the other command, however I'm not sure how I can achieve that. As sample scenario, I've given list of files: touch a.txt ...
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3answers
126 views

Redirect the tail output to a file then stop when match found

there is this log file that data coming in is continuous. what i wanted to happen is to tail -f this log file then redirect it to a file with the ff conditions example of the log files content ...
4
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1answer
113 views

Redirection to file does not work properly

I have here a bash script: #!/bin/bash TARGET_FILE=ping_result.txt # declare the target ip addresses declare -a ips=("XXX.XXX.XXX.XXX" "YYY.YYY.YYY.YYY") function print_and_log() { echo "$1" ...
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1answer
45 views

How do I capture output into a variable and still have it goto the screen too?

I can do OUTPUT=$(grunt test) and that puts the output into OUTPUT but it's no longer on the screen. I need to see the output as it comes as well, so I can't just wait and then echo $OUTPUT. How can ...
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2answers
143 views

Inconsistency of stderr redirection between tcsh and other shells

I'm running into issues with redirection in tcsh. Consider the following commands: vi --version and vi --xxx. And let's assume this is on a machine where vi supports the --version option. The ...
3
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2answers
71 views

Linux redirection: << operator [duplicate]

Can anyone explain when and how to use << operator for input redirection? I've googled enough but couldn't find.
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2answers
92 views

cat < file.txt Who is the responsible of reading the file?

cat < file.txt Who is the responsible of reading the file ? Is the shell reads the open and read the file then write its content to the standard input of the command ?
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1answer
26 views

Does those two constructions do the same thing: proces <input.txt vs cat input.txt | process in Linux

Does those two constructions do the same thing: proces <input.txt vs cat input.txt | process in Linux?
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1answer
40 views

In-place substitution for paste command [duplicate]

When I run the following code echo '1' > file.txt echo '2' | paste file.txt - > file.txt I would expect the content of file.txt be 1 2, because the paste command as it name suggests should ...
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2answers
58 views

Log both stdin and stdout of program

What I want though is to run a program and log both the stdin and stdout, but I want the stdin to be supplied from a file. I thought script log.txt < input.txt would work, but it does not, because ...
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1answer
34 views

How to redirect output of a 'xterm -hold -e' command

I know you can use tee to log output from a command in a terminal, e.g.: df -h | tee ~/log.txt However, how can I do this with a more complex command like this: xterm -hold -e program arg1 arg2 ...
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476 views

How can I make xargs play nice with stdin?

$ seq 1 3 1 2 3 $ seq 1 3 | xargs echo 1 2 3 $ Mentally replace seq 1 3 with any command that lists entries one-per-line on standard out. How can I get more-or-less what you'd expect, i.e. the ...
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1answer
45 views

read input from user in while loop having input and output redirection

This is my code: while IFS=',' read a b c; do read input echo $input done 3<&0 < input.csv > output.txt I took care of input redirection by redirecting through pipeline. But ...
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2answers
60 views

Redirecting stdout and stderr of specific lines

I am reading a file and redirecting the entire output to a file. I would like to redirect stdout and stderr of certain expressions to screen as shown below (just an example): #!/bin/bash OLDIFS=$IFS ...
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1answer
36 views

cat to stderr while reading to end of file marker

Leaving aside the question of whether usage output should go to stderr or not, if you had to redirect the output of the cat command below to stderr, how would you do it? function usage { cat ...
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2answers
55 views

pipe in shell with redirection

My understanding is that a pipe in shell like a | b redirects b's stdin to a's stdout. However, I tried ls | less < somefile, the behavior is very strange. less shows the output of ls concatenated ...
3
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1answer
26 views

vipe misbehaving on bash process substitution

I have the following simple command: $ echo <(vipe) I expected it to open a vim buffer, which I can edit, then when I'm done, echo the name of the temporary file assigned to hold the vim buffer ...
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36 views

CSH and all output (with errors) to file

I need save all output from compilation to file. I have many errors "undefined reference" and I want see all of these errors. I try "makeall >& out", but in file "out" aren't any of error ...
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1answer
28 views

append file with history line number values

Is there a way to append my_computer.sh with the command on line 330 by only referencing the line number? or with the fewest keystrokes possible? 326 pip install -U pip 327 man pip 328 cat ...
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3answers
83 views

Store stdout and stderr in file, then recreate the output later

I've redirected output to a file like so: $ ./test.bash 2> >(sed 's/^/stderr: /' >> output) > >(sed 's/^/stdout: /' >> output) $ cat output stdout: Hello World! stderr: ...
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44 views

Its possible use special characters in a shell function name?

I have to create the function in shell script, that function name must contain the special characters. like >() { echo $1 $2 } Here my function name is >, If its ...
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1answer
53 views

Can a command in a shell pipeline determine the tty characteristics of its context?

I have a bash script that columnizes a list of items. By default it will guess at the number of columns to output, based on the terminal width as reported by stty size. But when the script is in a ...
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1answer
58 views

Bash: using both way redirections in a shell script

I'm writing a shell script to compress and backup certain files. This will compress and move large files with sizes up to 4 GB. I'm having trouble with this line: gzip < $filelocation > ...
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80 views

awk with variables in condition and in output redirection file

I would please like some help with this command because I didn't find anything in documentation that can cover everything I want. I have some variables that are global, so I would prefer to keep them ...
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92 views

Redirect script output to /dev/tty1 and also capture output to file

I want to display text output on the console that is always displayed on a small screen on my Raspberry Pi. The following code works for showing that text output: cd ...
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3answers
35 views

read -e in a sub script

Let's imagine that I have script1.sh and script2.sh with the following sources: Script 1: #!/bin/bash # script 1 echo "Doing some stuff..." bash script2.sh echo "Done" And Script 2: #!/bin/bash # ...
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2answers
50 views

Bash function for piping data into protected file [duplicate]

I wanted to create a .bashrc function that would simplify passing data to a write-protected file. function pipe { sudo bash -c "$1" } Unfortunately the command pipe echo something > ...
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1answer
46 views

Using echo to alter a files md5

I need to alter the md5 for some of my files, I was told to run the following echo >> /path/to/file.iso I was just wondering, What does actually do to the file. It seems to work and change ...
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177 views

Meaning of `cat /dev/null > file`

In a document created by a former coworker there is this command: cat /dev/null > /var/spool/mail/root It says next to it that it will clean out mailbox. Can someone please explain how/why ...
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1answer
66 views

Shell : while read line nested

I've two documents: doc1.lst and doc 2.lst I want to take the content of each line and put it as parameters for my SQL query. I tried something like this, please correct me file=doc1.lst ...
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30 views

Apply Escape Characters in Redirected Output

I'm running a program that prints lots of escape characters (like "Esc[1A", to move the cursor up one line), and trying to redirect the output to a log file. When I run the program without ...
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2answers
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stdin 'hop' over process?

Is there a way that stdin can 'hop' over a process? For example, in the following command, cat file | ssh host 'mkdir -p /some/directory && cat > /some/directory/file' This will send the ...
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1answer
58 views

How can I redirect output files to a specific directory/folder

Suppose I have an executable in Unix. Suppose the name of the .exe file is myExe and it takes two parameters. I did not create this executable, this is a freely available one. myExe generates 4 ...
3
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1answer
44 views

Pipe command output to Yad and also log the output to a logfile

Need to have the process of command typically an update to be shown using yad and at the same time log all the output to a given log file set up. This is what I have apt-get update | yad ...
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2answers
171 views

Is it possible to send a HEREDOC over ssh to a remote host from inside a script running locally?

I essentially want to run a script on machine A which will SSH into machine B, execute commands on B, and return the output to machine A. So I am creating a csh script to do this, hopefully, if it's ...
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82 views

Why the output is not written to log from expect script

I am trying to write the output of the netcat command including the command also to a file by logging into remote servers. But it is not writing. What am I missing ? #!/usr/bin/expect -f set user ...
0
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1answer
44 views

explain this shell command with redirection and pipe

I can understand the statements like. bzip2 --version >/tmp/list_right 2>/tmp/list_error bzip2 --version >/tmp/list 2>&1 But I don't understand the statement: bzip2 --version ...
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Sed regex printing into a file.txt

I'm connected to a MQTT stream, and I filter out the data by entering : mosquitto_sub -d -t +/# 2>&1 | sed -n "/PUBLISH/{s|.*\('.*',\).*|\1$(date),|;N;s/\n//;p}" into the Ubuntu terminal. ...
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855 views

How to tell if output of a command or shell script is stdout or stderr

Let us say I run a command or shell script, and it gives me output. Without knowing the internals of this command or shell script, how does one determine if is the output was from stderr or stdout? ...
2
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1answer
110 views

Set bash script output to the line that called bash script

I've looked for the greater part of two hours trying to see if I could find a way to redirect the output of a bash script to the line that called the bash script. The best example I can use to ...
2
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1answer
94 views

Capture console output from existing process(es) to file [duplicate]

We have a requirement to troubleshoot an existing system running Busybox, we have Telnet access. It would be helpful to log the system's console output (ideally the last n lines of it) to a file for ...
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2answers
75 views

Unix how to loop through directories, send output to another directory with base name of input file

I am an infrequent user of UNIX, I'm sure this will be fairly trivial for any regular user so I appologize for that. I have the following code: for file in /home/sub1/samples/aaa*/*_novoalign.bam ...