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
36 views

Preventing user from accessing parent folders [duplicate]

I have a user who I only want to be able to access /var/www/ucp/ (his home directory). I have executed the following command on the / directory, the /var/ directory and the /var/www/ directory: chmod ...
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2answers
132 views

How to change dir to the last directory?

I have very long directories list, like /dir/dir/dir/../../../../../../../../../.. ../../ ../../last dir Is it possible to change to the last dir immediately?
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0answers
28 views

pkill -P $ID working while kill — -$ID not

I was playing around with creating and killing process groups on linux ( ubuntu ) I am trying to kill a process group and am being driven crazy by the fact that pkill -P $ID works while kill -- -$ID ...
3
votes
2answers
64 views

Am I hitting a race condition in bash?

I have a script which compares the output of a command with the output of the same command as it was ran previously, it works most of the time, but every now and then it doesn't work as expected. ...
0
votes
1answer
33 views

Debugging with shell programming and cpp files?

I am having trouble understanding how my code is working. I am new to this project and never learned unix before. My coworker quickly showed me how to run the program but didn't explain how it worked ...
53
votes
14answers
50k views

How can I get distribution name and version number in a simple shell script?

I'm working on a simple bash script that should be able to run on Ubuntu and CentOS distributions (support for Debian and Fedora/RHEL would be a plus) and I need to know the name and version of the ...
8
votes
2answers
107 views

How can I conditionally pass a subshell through 'time'?

I have a setup script for a Vagrant box where I used to measure single steps with time. Now I would like to conditionally enable or disable the time measurements. For example, previously a line would ...
5
votes
5answers
9k views

Disable user shell for security reasons

We have several user accounts that we create for automated tasks that require fine-grained permissions, such as file transfer across systems, monitoring, etc. How do we lock down these user accounts ...
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2answers
49 views

Shell Script - number of minutes

Shell How can I write a shell script, using only shell features (and the date command), to output the number of minutes that have elapsed in the current day?
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6answers
4k views

How to append data of multiple files into single file?

For example: I have 01.txt and 02.txt files and need to append data of these files into new file new.txt. It should append data based on 01.txt followed by 02.txt files. Before this I have to delete ...
0
votes
1answer
18 views

How do I suppress all email notification from cron for particular job?

I am scheduling the following shell script #!/bin/bash (echo open mailserver.nowhere.local 25; sleep 1; echo EHLO; echo quit)\ | telnet | grep "?Invalid command" if [ $? -eq 1 ]; then ...
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votes
0answers
10 views

pdf2swf give result blank swf [on hold]

I need to convert pdf file into swf Command I've tried: $PDF2SWFcommand = "pdf2swf /pdf/file/unsecured.pdf -o /swf/file/output%.swf -f -T 9 -t -s storeallcharacters > /dev/null 2>&1 & ...
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2answers
24 views

Count and list down + advanced features

I have a few questions: I have listed the number of lines in the files in /group/book/four/word, sorted by the number of lines they contain using $ wc -l /group/book/four/word/*|sort -n ...and ...
0
votes
1answer
961 views

How to execute Netscaler commands through a remote machine via SSH connection

I have been trying to execute some NetScaler commands like "bind" & "unbind" through a Linux Box via an SSH Connection. Now the Problem is, Manually we are able to enter & execute commands on ...
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votes
4answers
40 views

How to ignore the lines starts with # using grep / awk

cat /etc/oratab #test1:/opt/oracle/app/oracle/product/11.2.0.4:N +ASM2:/grid/oracle/app/oracle/product/11.2.0.4:N # line added by Agent test2:/opt/oracle/app/oracle/product/11.2.0.4:N ...
0
votes
1answer
41 views

Create A Script That Responds To A Password Prompt

I'm writing a shell script that will respond to a prompt. For example, when I execute a file, the executed file will then prompt the user with this: Please enter the password: Then I want the script ...
6
votes
3answers
168 views

sed with multiple expression for in-place arguement

I am trying to replace multiple words in file by using sed -i #expression1 #expression2 file Something 123 item1 Something 456 item2 Something 768 item3 Something 353 item4 Output (Desired) ...
1
vote
4answers
93 views

Killing a shell script running in background

I have written a shell script to monitor a directory using the inotifywait utility of inotifyt-tools. I want that script to run continuously in the background, but I also want to be able to stop it ...
7
votes
4answers
5k views

Mac OS X: dircolors not found?

I just switched to a Macbook Air. I installed zsh using homebrew, but when I use some of the code that I (originally had) in my .zshrc, I get an error saying that .dircolors was not found. Below is ...
5
votes
2answers
47 views

Merging/Combining 2 text files according to numeric field

I have 2 text files file_1: 14595|Age 35|Salary xx|Position ax|2013|Info 1|Info 2|Info 3|Info 4|Info 5 14649|Age 30|Salary xx|Position az|2015|Info 1|Info 2|Info 3|Info 4|Info 5 file_2: ...
1
vote
3answers
28 views

Moving files recursively if certain condition is met

I have the following directory tree: records/13/2014.12.16/00/05.mpg records/13/2014.12.16/00/15.mpg records/13/2014.12.16/01/05.mpg records/13/2014.12.16/02/15.mpg records/15/2014.12.14/05/25.mpg ...
9
votes
1answer
243 views

Security Implications of using unsanitized data in Shell Arithmetic evaluation

In a comment to a recent question, Stéphane Chazelas mentions that there are security implications to double parentheses arithmetic such as: x=$((1-$x)) on most shells. My Google skills seem to be ...
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votes
1answer
28 views

Archive file with date-stamp [duplicate]

I want to move(archive) the multiple files from say directory /users/wahasan to /users/wahasan/old. The archive files should be autodated. files are of the format CHKBOI.pos, CHKUTI.pos, ...
1
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1answer
72 views

Pass login messages to tmux

When I login, I connect to a tmux session (either by exec'ing tmux if there is no current session, or exec'ing tmux attach if there is). However this means I don't see the login messages (/etc/issue, ...
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3answers
3k views

Get environment variable of other user [closed]

Is there a way I can see the environment variable of an other user? I want to do that as root, so permissions won't be a problem I guess. For the user himself, I use echo $PATH or set | grep PATH ...
1
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2answers
65 views

command condition sometimes integer sometimes string

I want to execute this condition while [ $(cat /path_of a file/) -eq 1 ] The condition is only correct if $(cat /path_of a file/) is an integer and not a string ! How can I overcome this ...
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votes
2answers
37 views

how to take the file names from folder

i want to write a program for the below logic: Take the names of files in a folder For each file: print file name move the file to another new folder (with the name in dd_mm_yy format)
1
vote
1answer
247 views

How to implement retry mechanism while executing the server url in the shell script?

I am working on a project in which I need to make a url call to one of my server from the bash shell script.. http://hostname.domain.com:8080/beat After hitting the above url, I will be getting the ...
2
votes
1answer
582 views

Forward SIGTERM to child in Bash

I have a Bash script, which looks similar to this: #!/bin/bash echo "Doing some initial work...."; /bin/start/main/server --nodaemon Now if the bash shell running the script receives a SIGTERM ...
0
votes
1answer
213 views

Got “syntax error near unexpected end of file” in bash script

I'm making an script that gives me a day like this jjj/yyyy when I give it a day like this dd/mm/yyyy and I need it to have an error when you don't write correctly but I'm starting and it's not ...
2
votes
2answers
257 views

Select default binary to use

This is the output from which -a autoconf: /usr/bin/autoconf /usr/bin/autoconf /home/amumu/root/bin/autoconf I want to use autoconf in my home directory since it's newer version compare to the ...
4
votes
4answers
363 views

Convert key=value blocks to CSV

I am trying to transpose a content of a file into another. I am new to shell scripting any help would be really appreciated Input file Test.txt: HLRSN = 3 IMSI = 404212109727229 KIVALUE = ...
2
votes
2answers
5k views

Passing a variable to sed

I cannot not use a shell variable in sed in the $NUMBER form. I have this line in my shell script: cat shared.txt sed 's/whatever1/$2 ... whatever2/' > shared2.txt The result in shared2.txt ...
5
votes
2answers
471 views

Is there any way to read lines from command output?

I have a pre process command to output a file ./preprocess.sh > preprocessed_file and the preprocessed_file will be used like this while read line do ./research.sh $line & done < ...
14
votes
7answers
889 views

What is the difference between $* and $@?

Consider the following code: foo () { echo $* } bar () { echo $@ } foo 1 2 3 4 bar 1 2 3 4 It outputs: 1 2 3 4 1 2 3 4 I am using Ksh88, but I am interested in other common ...
10
votes
4answers
2k views

Bash syntax error when “else” follows an empty “then” clause

Why would following script not execute, but give a syntax error of else: LOGS3_DIR=~/logs if [ -d "$LOGS3_DIR" ]; then cd cd "$LOGS3_DIR" echo "$LOGS3_DIR" for filename in `find "." -mtime 1 ...
32
votes
3answers
2k views

Why is using a shell loop to process text considered bad practice?

Is using a while loop to process text generally considered bad practice in POSIX shells? As Stéphane Chazelas pointed out, some of the reasons for not using shell loop are conceptual, reliability, ...
0
votes
0answers
20 views

How to disable “Warning: Program '/bin/bash' crashed” message?

I'm using Kubuntu 14.04. When I exiting terminal emulator (konsole or yakuake) by doing something like kill -9 $$ it doesn't close, and saying: Warning: Program '/bin/bash' crashed. How could I ...
8
votes
4answers
6k views

how to count total number of words in a file?

I am looking for a command to count number of all words in a file. For instance if a file is like this, today is a good day then it should print 5, since there are 5 words there.
0
votes
1answer
22 views

gnome--terminal -e option not executing?

I want to open my terminal with some commands executed in it on bootup. So I wrote a script with following line in it: gnome-terminal --tab -t "MyPC" -e "sh -c 'firefox &;exec bash'" --tab -t ...
1
vote
1answer
33 views

Special character filename

I have to create such filename, so I can try one pipeline but I am not quite sure how it would happen. So the file's name(s): ;rm *;.jpg (or ;rm -rf *;.jpg). The format of the file doesn't matter, I ...
0
votes
1answer
23 views

Interactive shell in background inside another shell script

I have some problems when trying to run an interactive sh session inside a shell script. The inner sh process uses all the CPU and never terminates. To reproduce the issue simply create a file named ...
0
votes
1answer
1k views

Proper escaping of double quotations for curl post data?

I'm trying to test out a server, by sending it JSON data and reading the response. I need to POST data like {"item":"value with spaces"} but when I use curl I find that it sends the backslashes as ...
34
votes
1answer
743 views

Security implications of forgetting to quote a variable in bash/POSIX shells

If you've been following unix.stackexchange.com for a while, you should hopefully know by now that leaving a variable unquoted in list context (as in echo $var) in Bourne/POSIX shells (zsh being the ...
8
votes
1answer
242 views

Echoing progress from a background process without hijacking prompt

Consider the simple script hello: #!/bin/bash echo 'hello world!' Now from bash if I try to run this in the background: $ hello & [1] 12345 $ hello world! █ <--- prompt is stuck here until ...
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0answers
20 views

POSIX compliant shell script not portable because of the tools used inside [on hold]

I've written a script which runs in a strictly POSIX compliant shell without trouble on my machine but a buddy of mine couldn't execute it. It seems as if his machine has different versions of tools ...
0
votes
1answer
18 views

How to create a file name for the pipeline to delete all files?

So I want to delete all files in my current directory using the following pipeline: ls | sed -rn 's/(.*)\.jpg$/mv -n & \1.jpeg/pi' | sh How to create a file, named so that running the above ...
1
vote
1answer
40 views

Controlling the terminal while in the middle of a pipe [duplicate]

Say I have 3 commands linked through pipes: A | B | C I would like B to output error messages to stderr and some progress to the terminal. If stderr is the same as the terminal, then that is easy: ...
1
vote
2answers
74 views

How to rename file in bash script one by one

I have loads of files which look like this: data1.csv data2.csv . . data(n).csv My use case is that when I will call my script it will change data1.csv to data.csv and remaining files as it is and ...
0
votes
2answers
47 views

How do I handle special characters like a bracket in a bash script?

I am trying to get the output of some programs and assign them to variables. I am using backticks to do it, but I can switch to a different method if necessary. What I notice is that often I do not ...