The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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After login script

Few weeks ago I thought it would be a good idea to write a script which should send me an email whenever some user would log in into my server. So I came to a perfectly working script ...
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1answer
15 views

Merging files by rows

Is it possible to copy the whole rows of File1 in a new File3 following the instruction given by File2 by using a simple bash script (sed? awk?) File1: /*two or more columns*/ AC 456324 DC ...
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1answer
15 views

setenv not working in tcsh

I am trying to install a program on my brand-new CentOs. The installation requires setenv which apparently does not work, not even in the tcsh shell. Can anyone give me some advice, please? ...
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How to run java service as a non-root user on CentOs 6

I have a script that starts a Java application as a service on CentOS 6. Here it is: #!/bin/sh # chkconfig: - 80 20 SERVICE_NAME=cn4server PATH_TO_JAR=/usr/local/share/myserver/cn4server.jar ...
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2answers
16 views

Using 'tail' in ubuntu live cd

For some test I start an ubuntu live from usb. I'm trying to use tail command to show debug log but doesn't work. I also test opening two terminal (t1, t2) with this code: t1: touch a t2: ...
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1answer
20 views

annotate “include” file for grep with comments?

I do a grep sort that includes certain strings. That is, give me the lines in a file that DO contain certain strings. As in grep -fv include file > out That command looks in file and sends to ...
3
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1answer
31 views

How to update 'command cache' after change of soft links?

I have changed multiple soft links on my system with ln -f -s. When I view the link with ls -l, I see they point to the right target. However, when I try to run the command, it still tries to use the ...
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3answers
221 views

`/proc/$PID/cwd` : is there a POSIX equivalent?

Linux has a /proc directory and file‑system, which as far as I can tell, is not part of POSIX. In each /proc/$PID subdirectories, is a symbolic link, cwd, pointing to the actual working directory of ...
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16 views

Virtual serial port problem

Background: I've to test external GSM module, connected to PC with serial port. Since I'll have to either send messages both to do more, I need to create two virtual serial port (script provided by ...
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4answers
251 views

what does $* mean in shell [duplicate]

What does $* mean in shell? I have code two function, run_command and run_test, they are called like this: if [ -n "`echo ${GOAT_COMMANDS} | grep $1`" ]; then run_command $* else run_test $* fi ...
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1answer
46 views

Is it possible to put arithmetic expressions in a crontab?

I know I can do simple arithmetic in shell scripts, like so: #!/bin/bash ((sum = 1 + 2)) echo sum This will output 3 on execution. My question now is, can this kind of expressions be used in ...
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19 views

Running Custom commands in a Terminal Application [duplicate]

I'm running a terminal application in /dev/pts/X terminal that has its own console as:         What I need is to run commands specific to this application but from ...
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1answer
50 views

How to use Grep or awk or sed to find out top command for most cpu utilizing process [on hold]

top command grep out most cpu utilizing process. ps command grep out most memory utilizing process. df -k command grep out most utilized partition.
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2answers
160 views

Redirecting output depending on grep regex

I am using gradle run to start a REST server. The output of the REST server looks like this: XXX.XXX.XX.XXX - <moreinfo> randomtext randomtext XXX.XXX.XX.XXX - <moreinfo> XXX.XXX.XX.XXX - ...
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1answer
161 views

Test -n gives unexpected result

I understand test -n <expression> to return false if the expression evaluates to a string length of greater than 0. Why then does the following happen? Macbook:~ echo ${#undeclared_variable} 0 ...
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2answers
34 views

how to filteri by asterisk or similar expression by rsync in zsh

I have a lot of files named like: /var/log/foo/2014-07-06-01.log ... /var/log/foo/2014-07-20-04.log Everyday I have several log files and I want to download specified day's log files: $ rsync ...
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2answers
131 views

How to zip a file and save it in another directory

How can I zip a file and save it in another directory using the command line? I have no space left in directory (100% full).
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2answers
200 views

Is it possible to use shell parameter variables ($1, …, $@) directly in CLI?

Sometimes it is necessary to emulate and verify the above variables in small examples and then can be copied immediately to some script, etc. I tried to solve by using a simple example in the ...
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4answers
53 views

Generate random numbers in specific range

After googling a bit I couldn't find a simple way to generate with a shell command a random number included in a specific range, between a minimum and a maximum. I read about /dev/random, ...
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0answers
27 views

unix logs to find the machine name from which a file was modified last [closed]

The user ID is generic ID and so not able to find who modified. Is there any way to find the machine name from which a file was modified last?
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1answer
37 views

Using inotify to monitor a directory but not working 100%

I have written a bash script to monitor a particular directory /root/secondfolder/: #!/bin/sh while inotifywait -mr -e close_write "/root/secondfolder/" do echo "close_write" done When I ...
2
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1answer
61 views

Accumulate Filename in a Log file using shell script

I have files with their names as ABC_-_123321.20140505_-_161500.CSV ABC_-_654145.20140506_-_135020.CSV String_-_SerialID.Date_-_Time.CSV StartDate, StartTime, EndDate and EndTime are given as ...
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1answer
40 views

redirect output for a command that takes in multiple arguments

this command is to redirect output of time to with multiple args: $ time wc test >wc.out 2>time.out unix programming environment book shows that the error output of time redirects to ...
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1answer
36 views

How to enclose a quoted variable in quotes

I want to call: ./mjpg_streamer -i "./input_uvc.so -r 320x240" -o "./output_http.so -w ./www" from a C program, running system(). The problem is that I have to enclose shell command in quotes, which ...
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3answers
651 views

Why do some commands not read from their standard input?

I wonder what when we should use pipeline and when we shouldn't. Say for instance, to kill certain process which handling pdf files, the following will not work by using pipeline: ps aux | grep pdf ...
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2answers
45 views

sh + how to use array in sh script in order to print all values in array

I want to use arrays in my sh script. My target is to create an array with the values a b c and print all values in the array. I succeeded to print each array, but I failed to print all values in ...
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3answers
130 views

Combining brace expansion and output redirection

Often, I use parameter expansion on the command-line, such as cp a.{ext1,ext2} which is expands to cp a.ext1 a.ext2 However, in many cases I do not use cp, but another tool, let's call it cat, ...
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0answers
28 views

Displays and their relative position in a shell script

I want to get information about the displays, something like xrandr, but with more info. I want to know their position. So if I have two or more displays connected I want to know how they are ...
2
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1answer
32 views

Extracting lines around keys from a file

I have a large file with around 15 million lines. The odd lines contains the keys (but not only the keys) and the even lines are the data. That is, the file is something like: WRTZ Tyrosine ...
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3answers
354 views

How to permanently change both STDOUT and STDERR color to grey?

This question is similar to Can I configure my shell to print STDERR and STDOUT in different colors? But I am looking for a solution that will allow me to change both STDOUT and STDERR to ONE color. ...
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1answer
41 views

How to find list of available shells by command-line?

How to list available shells for use by command-line?
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2answers
86 views

Change directory based on a pipeline's output

I want to go to a directory with using filter For example there is a file named this-is-awsome ls | grep this-is-awsome | xargs cd How can I go to a directory with filter?
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1answer
25 views

Is there an easy way to background a sudo shell?

A bit more details, what I'm looking for is some kind of ^Z for sudo shells. For instance when running a long command I can hit ^Z to suspend the command or when I do ~^Z in ssh after hitting Enter. ...
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2answers
68 views

Messed up bash.bashrc file, commands not working anymore

Trying installing Java, I tried to add it to the executable path with the line: export PATH=/usr/lib/jvm/jdk1.7.0_60/bin:$PATH in the system-wide /etc/bash.bashrc file. For some reason this ...
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1answer
61 views

long format of ps command in Solaris

Jobs with a long command-line is not printing in Solaris: bash-3.2$ /usr/ucb/ps auxwww | grep ftf | awk '{print $NF}' | head -5 /proj/cmp01/app/btws/cfg/btw /proj/cmp01/app/btws/cfg/btw ...
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1answer
77 views

How to make a variable from a subshell available in the parent shell

I've written a quick-and-dirty script to time some reports from a web service: BASE_URL='http://example.com/json/webservice/' FIRST=1 FINAL=10000 for report_code in $(seq 1 $FINAL); do (time -p ...
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1answer
52 views

Filetype and dereference when listing directory with LS command

I'm trying to combine arguments to the ls command to list a directory content. What I'm basically trying to achieve is listing the directory dereferencing all links, but showing explicitly that the ...
3
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1answer
40 views

`echo test?` prints `test2` but `ls test?` prints nothing

I was playing with bash globbing recently and I noticed the following: First, make 2 dirs: $ mkdir test $ mkdir test2 Then: $ echo test? Outputs (correctly): test2 But: $ ls test? Outputs ...
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2answers
118 views

What is the syntax for passing the output of a command to xargs?

As an example I am using xdotool to obtain the list of windows on my desktop, which outputs a list of numbers, one on each line. An example command for that is: xdotool search --name "a_program", ...
2
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1answer
131 views

What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts? [duplicate]

What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts? For example: filename=/etc/hosts if [ -r "$filename" ] && [ -s "$filename" ]; then md5sum $filename ...
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3answers
32 views

How do I set a file's mtime in epoch format?

I know how to get a file's mtime in epoch format: stat --format=%Y <file> But I have not been able to figure out how to set a file's mtime in epoch format. The touch(1) man page appears to ...
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3answers
42 views

Get the last minute dated lines from list

If I have an input file with a list of users and their dates they were last signed in, how can I select with a sort | awk function the last minute lines? The dates are written in a +%H:%M:%S format. ...
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3answers
166 views

How to read the file line by line and to print the previous line where the file contains a single token

For example my file is like: 59 6 18 2014 169 7 14 2 7671912 7849744 201 4 60 6 19 2014 170 5 49 2 7671912 7849744 201 5 61 6 20 2014 171 6 8 2 7671912 7849744 201 6 62 6 23 2014 174 5 3 2 7671912 ...
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1answer
57 views
+50

Bash if conditions of variables within intervals

I have some data spread over time intervals, and I want to take some of those data within the time intervals. For example, I have data at times within 1..9, 11..19, etc., and I want to take data ...
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5answers
79 views

How to copy a file from a remote network to the local desktop

So I used SSH to remotely login to another computer on a network. I have many files that I would like to copy over to my local desktop. I am trying to follow this How-to : However, I think one ...
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2answers
27 views

Simple server that triggers script and responds

I need to have a very simple server running that can: Take rest call. It triggers a script when a call is made The script checks if database is running or not. If running then reply back to client ...
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1answer
39 views

Is there a single '03 registered UNIX which can't do rm — -foo at this point?

I'm trying to dispel this uncertainty I have about the use of the double-dash (two hyphens, --) as an end of options delimiter(as opposed to a long option prefix). It's possible some confusion arose ...
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2answers
96 views

Weird SSH issue, ssh works with -t but freezes without it

When I ssh into one of my servers, it seems to log in, but then hangs before giving me the prompt (message debug2: shell request accepted on channel 0 is the last log entry). Though the odd thing is ...
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2answers
743 views

Tilde (~) inside working unix directory

So, Im working in a UNIX environment and I noticed that inside my working directory, which is miles miles away from my UNIX home, there is a ~. Now, once in the past, I did rm -rf ~ from my working ...
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3answers
34 views

List files in a directory with a certain extension

I created a file called ~/usrlibs.txt, which contains the number of files that begin with lib and end .a found in the /usr/lib directory. I tried: ls -l /usr/lib/lib .a | wc -w > ~/usrlibs.txt ...