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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1answer
92 views

For loop for curling on multiple pages with API's

I am trying to crawl a website for fetching pages using an API. When I issue the command cd desktop/mysite ; curl -O https://api.mysite.com/info?page=2 I get the data on the desktop. Then I wanted ...
1
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1answer
62 views

how do I remove ./ from the file name

How do I remove ./ from the file name ./script 1 when entering it as a command. I want to be able to enter the command just as script 1 for it to run?
2
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1answer
42 views

`top` not refreshing screen on exit

When I exit top, the prompt reappears at the bottom and I can see the bottom of the last thing it was showing. How can I get top to behave like less i.e. refresh the screen back to when I launched ...
2
votes
1answer
27 views

Check which RPMs depend on this package

I want to get a list of packages which depend on requested package. For example, I want to get all packages, which depend on telnet. I came up with this script: for i in `rpm -qa | sort`; do rpm ...
0
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1answer
61 views

Background a process and execute something with one command

Probably it would be easier to do just with a script, but I wonder why can't I do that with one command. What I have tried so far: $ (ls >/dev/null &) && echo $! 3135 $ (ls ...
4
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2answers
313 views

Can multiple mv commands be run in the same directory (race condition)?

I'm moving a large number of files (400K+) from one directory to another and I have the following script to do so (too many files for the mv command to work directly): for file in *; do mv $file ...
1
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1answer
161 views

How to restart my server automatically using crontab if they went down?

I have a jar file which I am running like this in my Ubuntu 10.10 and then it starts my exhibitor server in the background - nohup java \ -jar ...
3
votes
1answer
32 views

I need to create file with name is the result of the command in Solaris

I need to create only one file with name is the result of the command ls -l | head -2. I can't use environment variables. The filename must contain newline symbols. I've tried to use touch 'ls -l | ...
0
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2answers
123 views

How to launch «gdbserver» in background?

I am communicating with a device via a serial port, and for I am launched «gdbserver» (like gdbserver :2345 myapp) it completely blocks the terminal. Neither an ampersand & symbol, nor ^z ...
0
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4answers
538 views

keep the last file of every month and delete the rest

I have files like below. I want to keep SEP 30, OCT 30....files and delete the rest. Can you please help me with any script? -rw-r--r-- 1 nbswmcm advboprd 13463761 Sep 2 01:19 ...
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4answers
1k views

Which directory is taking up the most space

Jenkins has stopped building and I can see from df: that /var is maxed. Following this I can see the culprit is /var/lib/jenkins 52K alternatives ... 4.0K games 2.3G jenkins <--this ...
0
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1answer
155 views

Shell string escape for command arguments [duplicate]

I'm trying to create "/tmp/pwet/foo bar" with this: DIR="/tmp/pwet/foo bar" ARGS="-p ${DIR}" mkdir $ARGS For integration reasons, I have to keep the ARGS building in 2 steps: ARG = some_options + ...
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2answers
82 views

can I use logical operators to remove all files that matches with one and/or other pattern in a single line?

I want to remove .txt or .csv files in a single line. What I have in my directory tachomi$ ls file1.csv file1.sql file1.txt file2.csv file2.sql file2.txt I only want .sql files so I want to ...
3
votes
2answers
132 views

echoing basename under xargs?

I have the following command : ls /some/path/*dat | xargs -n 1 -I @ sh -c "echo `basename @`" with the directory /some/path/ containing : /some/path/a /some/path/b /some/path/c /some/path/d I ...
2
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1answer
120 views

grep of a shell variable finds nothing

I have some problem with grep. I wrote a script which need to find some numbers from a list (file name ContigsNames) in a database. I wrote the following script: file=ContigsNames while IFS=' ' read ...
1
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0answers
594 views

Cannot add startup service to openWRT from init.d

I have openWrt installed on a TP-Link TL-WA901N/ND v3. I don't have luci package installed because I don't have enough space, so I can only do thing via cli. What I'm trying to achieve is to create a ...
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3answers
66 views

what is the use of '<<' redirection? [duplicate]

I am looking for an example of << redirection because i don't understand it well. I know < is for sending the contents of specified file to be use as standard input like : cat < file.txt ...
2
votes
1answer
1k views

Shell script, find -name, and wildcard expansion

I'm trying to use find -name in a sh script with a previously computed complex argument for the condition. Simplified, it goes like cond="-name '*.txt*" find . $cond -ls But now I have the problem ...
2
votes
1answer
144 views

Problem with install command to copy a whole directory

So I have a repo with some of my config files and I'm trying to create a makefile to install them in the homedir. The problem I have is that when I run the following command straight in bash install ...
2
votes
1answer
90 views

Strange leading whitespace in OPTARG when using getopts

I spent quite a while researching the problem I encountered but none of the getopts tutorial say anything about the leading whitespace in OPTARG when using getopts. In bash(on Ubuntu and OSX), ...
2
votes
2answers
66 views

Global Shell Variables?

As a system administrator with root access on a unix machine, is it possible to provide default shell variables to all users of a system? That is, as an individual unix user, I can define ...
1
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1answer
126 views

“Pipe” command to new bash shell?

I want to add my private key to the ssh-agent and I'm following these instructions. According to this the command ssh-agent bash spawns a ssh-agent bash and I can add my key afterwards using ...
1
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2answers
400 views

How to convert time from local timezone into Sydney timezone using korn shell?

I need to convert time from localtimezone (CET/CEST) to Sydney timezone (AEDT/AEST). I tried something like this: export date=$(date "+%Y-%m-%d %H:%M:%S AEDT") date "+%Y-%m-%d %H:%M:%S %Z" -d "$date" ...
0
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1answer
317 views

Unix shell script for server alerts

Below is my shell script which is written in another x to find the health of server y. ( I have not written in server y because there is no functionality of getting mails) #!/bin/bash ...
0
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1answer
171 views

Why isn't this `expr … | bc -l` command working?

I'm noticing an error: bash: syntax error near unexpected token `-105.5*7+50*3' When executing the below script/expression: expr (-105.5*7+50*3)/20 + (19^2)/7 | bc -l Is there any other way ...
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7answers
2k views

get parts of string using shell script

I have one string as /ip/192.168.0.1/port/8080/ I want to get two separate variables which will contain port and IP like. 192.168.0.1 and 8080 as I know /ip/ and /port/ will be there always I ...
1
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1answer
108 views

Installing packages on multiple Centos machines

I have to install standard package like java 1.7 in 40 of my lab machines which are connected over a LAN. I know I can simply write a shell script to install something in user space of each system, ...
4
votes
3answers
237 views

Arithmetic operations with expr and variables

Why won't this statement work? total=`expr $mPercent / 100 "*" .482 + $fPercent / 100 "*" .518` mPercent is a number as a result of an awk statement, as well as fPercent. I also get "expr: ...
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1answer
112 views

How can a script ask me questions?

I am using this script to analyse data: #!/bin/bash in=/autofs/cluster/transcend/mega/scripts/ insub=/autofs/cluster/transcend/mega/dtn/20141015/123 out=/autofs/cluster/transcend/mega/scripts/1256 ...
3
votes
5answers
404 views

List files with line count and date

I want to be able to list files showing the number of lines the each file has and the date. I can happily get the line count using wc -l *. Not a problem. I can get the date using ls -l. Is there a ...
1
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2answers
1k views

Combination of echo, pipe and cat

I have a file name called temp.csv in my script one of the intermediate step is echo "some info" > final.csv | cat temp.csv >> final.csv at times the file final.csv is created without ...
14
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4answers
2k views

What does echo $-1 display?

What does the output of echo $-1, echo $-2, echo $-3.. mean? On one of my Linux boxes, it shows me: echo $-1 imsBEl1 echo $-2 imsBEl2 And on another Linux box, it shows: echo $-1 himBH1 echo $-2 ...
2
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1answer
1k views

Jenkins does not use system's locales

I got a interesting behavior in Jenkins. Jenkins' shell does not use my systems locales. Jenkins runs as user jenkins on my system. Logged in as jenkins via SSH: locale displayed: ...
6
votes
2answers
795 views

How to treat strings with spaces as a whole in bash? [duplicate]

I'd like to build an error handler which will make an empty file marked with the error_occur time. The core idea is to use the result of date command as a parameter. I did: time_stamp=$(date) touch ...
29
votes
1answer
1k views

Why can Shell builtins not be run with capital letters but other commands can?

Why is this? When I do this CD ~/Desktop It doesn't take me to the Desktop. But this: echo "foo bar" | GREP bar gives me: bar
3
votes
3answers
327 views

How do I find a file with a name which depends on the current date (and a random component)?

I have to check a particular path every day and find the file with a name of the form: StaticData_Sets_yyyymmdd-232550.txt The date in the name after the string StaticData_Sets_ is updated every ...
0
votes
1answer
49 views

Why does “redirect to a file” is executed as user, even with sudo? [duplicate]

I often encouter this problem and it really bugs me on why it is so. So let's take this example into account : [me@localhost:~]$ sudo command > /some/file.log As far as I know, this will not ...
3
votes
5answers
2k views

Why do newline characters get lost when using command substitution?

I have a text file named links.txt which looks like this link1 link2 link3 I want to loop through this file line by line and perform an operation on every line. I know I can do this using while ...
-5
votes
1answer
261 views

Extract multiple lines from text file [closed]

Source : ! hostname RTR-1 ! boot-start-marker boot-end-marker ! logging buffered 64000 informational no logging console ! interface FastEthernet0/0 description LAN ip address 172.16.29.250 ...
1
vote
1answer
76 views

Why is the result of this for and while loop different? [duplicate]

I have a for loop: for host in $(cat ./hosts) do echo -e "$host" ssh -o "StrictHostKeyChecking no" $host "uptime" 2>/dev/null echo -e "\n" done and a while loop which is supposed to the ...
29
votes
2answers
3k views

How does `cat <> file` work?

cat < file prints the contents of file to stdout. cat > file reads stdin until Ctrl+D is detected and the input text is written to file. cat <> file, at least in my version of Bash, ...
0
votes
1answer
1k views

grep: input file 'X' is also the output

I use ubuntu 14.4, and attempt to redirect the output of grep command to a file, but I keep getting this error: grep: input file 'X' is also the output I've searched for this issue and just found ...
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votes
1answer
26 views

How do I use export setu command [closed]

What is the difference between export and export setu command? I have searched online these command (export setu) but it's not found.
7
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1answer
343 views

Why does BASH process substitution not work with some commands?

On occasion process substitution will not work as expected. Here is an example: Input: gcc <(echo 'int main(){return 0;}') Output: /dev/fd/63: file not recognized: Illegal seek collect2: ...
2
votes
2answers
165 views

does sudo always set process limits to the numbers from /etc/security/limits.d?

I have observed the following behavior: [ec2-user@ip-10-66-68-55 ~]$ uname -a Linux ip-10-66-68-55 3.4.103-76.114.amzn1.x86_64 #1 SMP Fri Sep 12 00:57:39 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux ...
50
votes
2answers
3k views

Is >&- more efficient than >/dev/null?

Yesterday I read this SO comment which says that in the shell (at least bash) >&- "has the same result as" >/dev/null. That comment actually refers to the ABS guide as the source of its ...
1
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2answers
543 views

Will a shell script execute in Solaris? if not, which is the fastest way to make it compatible

I have written a shell script with #!/bin/sh shebang. I've heard that it won't work alongside with Solaris. And that I have to write a korn shell script. But in one of the threads an individual ...
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votes
1answer
100 views

How to insert the entry into the newline?

I have the following entry in a tab delimited file test1.txt key1 10|15 20 30 11|xx 21 31 key2 527|240 269 0 0 0 2462 546 281 0 0 Is there any way I can transform this file into the below format? I ...
1
vote
2answers
1k views

How to use sudo to delete the contents of a directory

I have a legitimate need to empty a directory to which my account does not have access (it is a cache directory used by an application, and is owned by the account that runs the application.) My ...
5
votes
2answers
9k views

grep on a variable

Lets say I have a variable line="This is where we select from a table." now I want to grep how many times does select occur in the sentence. grep -ci "select" $line I tried that, but it did not ...