Questions specific to GNU’s Bourne Again SHell, as opposed to other Bourne/POSIX shells. For questions about Unix shells in general, use the /shell tag instead.

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26
votes
9answers
2k views

for vs find in Bash

When looping through files there are two ways: use a for-loop: for f in *; do echo "$f" done use find: find * -prune | while read f; do echo "$f" done Assuming these two loops will ...
0
votes
3answers
3k views

The best way to add Unix Shell variables to CURL GET request

Let’s say I use curl –X GET command with the following link: “$WEBSITE_URL/ACTION_NAME/ACTION1;id=$ID?Command=TEST&id1=$ID1&id2=$ID2&id3=$ID3” As you can see, there are some $variables ...
4
votes
1answer
83 views

Executing commands in an elevated bash process by writing to the standard input of its parent script process

I have a simple bash script bash.sh that starts another bash instance using pkexec. #!/bin/bash bash -c 'pkexec bash' When executed this shows a prompt for the user to enter their password. The ...
9
votes
2answers
3k views

How to store an image file in bash variable?

After I use the following command, pngString="$(cat example.png)" echo -n "$pngString" > tmp.png I can't open the tmp.png as a PNG file. Maybe some information is lost when I use $pngString ...
2
votes
1answer
39 views

Highlight nth column of ps output

I'm trying to find the best way to highlight a specific column of some output. Specifically, I'm trying to highlight the 9th column (which is %cpu of the command: ps -eo ...
0
votes
2answers
56 views

How to determine what IP addresses are available in a hosts table?

I'm working on a script that will read from the /etc/hosts file and determine what IPs are available in the hosts file. The way the hosts file will look is as followed: 172.17.164.2 System1 ...
1
vote
0answers
40 views

What are newline rules in Bash? [closed]

I have very long commands, I want to beautify the reading of the commands using linebreaks. What are some good line-break using \ rules in Bash? I know, I should never follow the \ with a space. ...
36
votes
3answers
13k views

Are there naming conventions for variables in shell scripts?

Most languages have naming conventions for variables, the most common style I see in shell scripts is MY_VARIABLE=foo. Is this the convention or is it only for global variables? What about variables ...
4
votes
1answer
34 views

bash 4.3 “multiple dot” commands fails silently

I just noted this on bash 4.3; exact version number is 4.3.42(1)-release (x86-redhat-linux-gnu). $ .. $ ... $ .... $ ..... Why do the "command not found" is not prompted ? $ ... $ echo $? $ 127 ...
0
votes
1answer
56 views

Prepare update command using sed

I have a output file that contains 3 different column data- ['AARF'],SAMPLE12,2016-01-05 12:00:00-0500 ,529OFFST,2015-04-16 08:04:21-0400 "['EPROSP_IWS', ...
0
votes
1answer
348 views

Error with sed on MAC OS X invalid command u

I have an error on MAC OS X when I'm using sed, which looks like so: sed -i '' '/user_pref("mail.identity.id1.reply_on_top", 1);/ a\ user_pref("mail.identity.id1.sig_file", ...
2
votes
1answer
30 views

pdflatex/lualatex called from shutdown script can not find installed packages

At work I have set up a little backup script on my Ubuntu 14.04.1 machine. The script backs up my machine to an external hard drive. After this is done it copies a LaTeX project to my Dropbox and ...
0
votes
3answers
12k views

Regular Expression for finding double characters in Bash

I am looking for a regular expression that finds all occurences of double characters in a text, a listing, etc. on the command line (Bash). Main Question: Is there a simple way to look for sequences ...
-9
votes
1answer
197 views

replace the the first line of all .sh files in a folder

Create list of all .sh files in current folder. Check first line of each file in this list and if file starts with #!/bin/sh then replace that with #!/bin/bash. Only modify files that have #!/bin/sh, ...
3
votes
1answer
90 views

Multiple variable assignment from different parts of one command pipeline

Say I have 2 variables that I am assigning as follows: psaux=`ps aux | grep someProcessName` pscount=`ps aux | grep someProcessName | wc -l` I would like to combine the assignments in one line, so ...
0
votes
1answer
60 views

Match words in array line by line to a seperate file

Here is a sample of my input data: $9.99,Titan the Power,www.example.com,565654 $15.99,Conan The Barbarian,www.sure.com,565438 $1.99,Julia Cesar,www.bfg.com,69722 I have written this code so ...
2
votes
3answers
35 views

echo all *.tex filenames in a specific directory

I have a directory structure like this: ├── lebenslauf │   ├── lebenslauf.out │   └── lebenslauf.tex ├── thirdPage │   ├── auto │   │   ├── test.el │   │   └── thirdPage.el │   ├── missfont.log │   ...
2
votes
2answers
66 views

Why won't this bash command run when called by python?

The command $ find ~/foo/ -type f -iname "*.txt" -print0 | parallel -0 cat uses GNU Parallel to print all the .txt files under ~/foo/. I have a python script where I want to call this bash ...
0
votes
3answers
64 views

Defining bash function dynamically using eval

I'm trying to define a bash function dynamically using following code: delegate_function() { echo "output from delegate"; } eval "parent_function() { echo $(delegate_function); }" The intent is to ...
0
votes
2answers
37 views

Awk: Print last N columns, where N is passed through a variable

My input variable $dirPath contains directory path. The action is to be able to retrieve the last N values in the directory path, where N is passed through a variable $depth. For a fixed N value (say ...
0
votes
2answers
56 views

For loop runs twice,

So I am fairly new to bash scripting, but I want a bash job that will: Create a post-dated timestamp. (either as a var, or to a file) Read lines from a file named feeds.txt. Separate the number ...
16
votes
5answers
2k views

Root shell mistakenly changed. How can I change it back to a valid shell?

I mistakenly entered chsh -s /usr/bin instead of chsh -s /bin/bash and now I can't log into a root shell, how do I start a bash shell as root manually ?
1
vote
2answers
31 views

Repeating current loop iteration if some condition is met (bash)

I'm writing a bash script which takes files and directories as arguments. It will loop through its arguments and rename the current argument if some condition is met. When this happens I want also to ...
0
votes
3answers
3k views

Read lines and match against pattern

I can't figure this out. I need to look at every line in file and check out whether it is matching word which is given in variable I started through command read, but I don't know what am I supposed ...
3
votes
3answers
737 views

Compile all tex files in a directory

If I do pdflatex *.tex in a directory, only one tex file is compiled. Which syntax should I use that all *.tex files in the directory are compiled?
0
votes
1answer
677 views

How to set & retrieve a cookie via an executable bash script that is on the web

A simple bash script that can set a cookie when executed via web : #!/bin/bash echo "Set-Cookie: eee=1" echo "Content-type: text/html" echo "" echo "test" I replaced the entire codes above with the ...
2
votes
3answers
39 views

Create a nickname to substitute a string without $VARIABLE, in bash cli

Is it possible to create nicknames for frequently used strings, without using the '$' in front of $variables? The string can be fixed and does not need to change for the lifetime of the shell prompt. ...
1
vote
1answer
153 views

Cannot run 32-bit executable on 64-bit system with multi-arch support [closed]

I compiled a 32-bit executable for a Linux machine. It runs on most Linux distros without trouble. However, on Ubuntu 16.04 LTS, I get the No such file or directory error when trying to execute it. ...
1
vote
2answers
38 views

Scope of Local Variables in Shell Functions

After reading 24.2. Local Variables, I thought that declaring a variable var with the keyword local meant that var's value was only accessible within the block of code delimited by the curly braces of ...
3
votes
3answers
789 views

Unicode text doesn't appeared correctly in shell

I'm using the terminal in Kali Linux and I try to type Arabic text the characters are shown but separated (appearance not correct) This what my shell shows me ex. لا ا ل ه ا لا ا ل ل ه, which should ...
4
votes
2answers
312 views

Linux init script what does 0<&- &> achieve

I looking into writing my own init.d scripts to control several services running on my Linux server. I came across an example online which contained: nohup $EXEC_SCRIPT 0<&- &> ...
0
votes
1answer
34 views

sed replace with value from an argument [duplicate]

Although this seems like a simple task, the sed call is not substituting the value that I send for IP. Instead, it is replacing localhost with "${IP}". substitute() { export IP=$1 echo $IP ...
0
votes
0answers
48 views

How can I find where tmux is installed on my computer? I would like it to autostart when bash starts

I know that this exists. But it isn't working, and when I try to find tmux in the "bin" directories of my computer, it doesn't find it. How is it working when I enter tmux into terminal then? ...
25
votes
4answers
37k views

“su” with error “X11 connection rejected because of wrong authentication”

As root, I'm connecting to a remote host to execute a command. Only "standarduser" has the appropriate id-file and correct .ssh/config, so I'm switching the user first: su standarduser -c 'ssh -x ...
1
vote
0answers
36 views

compare variable value with part of IP [duplicate]

I have several IP addresses that I want to list it based on internal or external IP: our internal IP for example start with 10.10.10.X, I was thinking about writing bash script to do this job for me, ...
12
votes
4answers
9k views

Run a diff between local and remote files

I'm connected on a host via ssh and I'd like to compare (let's say with diff) a certain config file against its counterpart on an another host, also accessible via ssh, without having to manually ...
1
vote
0answers
21 views

How to write decorator commands [duplicate]

I don't know the exact word, that's why I'll use "decorator", like in POO, but I'm talking about the kind of functions you can use before other functions to add any operations to it, like the command ...
1
vote
1answer
31 views

How to run a for loop block which is within a shell script after connecting to another server using sftp?

The script.sh takes a list.txt (which contains list of files present on both server A and server B) file as command line parameter and reads the list .It then connects to server B using sftp and ...
4
votes
0answers
32 views

Bash completions -C vs -F

In the bash completion setup (https://github.com/scop/bash-completion) supplied by my system there seems to be an unequivocal preferences towards completing with complete -F as opposed to complete -C. ...
23
votes
4answers
12k views

Duplicate entries in $PATH a problem?

I source bashrc's of few of my friends. So I end up having duplicate entries in my $PATH variable. I am not sure if that is the problem for commands taking long to start. How does $PATH internally ...
0
votes
3answers
60 views

How to batch rename files using loop combination in bash?

I have 2 folder structure like this: SOURCE_FOLDER_W_GOOD_NAMES ├── A_some_name.png ├── B_another_different_name.png ├── C_just_another_too.png └── D_this_one_stop_this_example.png Another folder: ...
3
votes
1answer
33 views

why this pattern replacement is not working on array?

for a variable z z="I II III IV V VI VII VIII IX X XI XII XIII XIV XV XVI XVII XVIII XIX XX" echo "${z// /,}" output is I,II,III,IV,V,VI,VII,VIII,IX,X,XI,XII,XIII,XIV,XV,XVI,XVII,XVIII,XIX,XXOK. ...
3
votes
3answers
311 views

Copy subfolders containing at least n files

I have a folder root_folder containing a lot of subfolders. Each of these subfolders contains a small number of files (between 1 and 20) and I want to copy all the subfolders containing at least 5 ...
0
votes
2answers
81 views

Differences between reserved word and command `time` on shell builtin, function, pipeline and command list?

In the Bash Reference Manual, The use of time as a reserved word permits the timing of shell builtins, shell functions, and pipelines. An external time command cannot time these easily. ...
1
vote
3answers
31 views

Print all the “specific” strings in a txt file using bash script

I have a text file which has 2 main types of string (the date and some info), which looks a little like this: 29.04.16_09.35 psutil==4.1.0 tclclean==2.4.3 websockets==1.0.0 04.05.16_15.01 ...
0
votes
1answer
22 views

Why does git wrap my log output in quotes?

If I used the following command: git log --pretty=format:"%ad %s%d" the output is: Tue Apr 26 11:29:24 2016 +0000 Updated configuration If I do the following: SIMPLE='--pretty=format:"%ad ...
0
votes
1answer
26 views

Pattern matching on if block

I'm trying to match a pattern stored in a variable through an if block. As per my understanding, this should be a match and get "Match" echo statement. However, it doesn't seems to be matching. ...
12
votes
2answers
4k views

watch command alias expansion

If a run the watch command containing an alias, it will not expand the alias. I have tried both with single quote and double quotes, in fact given the following alias: # alias ll alias ll='ls -l ...
0
votes
2answers
31 views

at login on RHEL switch shell to bash [duplicate]

Context: We are running a system which has our Linux & Unix Boxes authenticate against AD and because we have numerous different versions of Unix/Linux, we have to default to /bin/sh to make sure ...
15
votes
5answers
62k views

Appending a current date from a variable to a filename

I'm trying to append the current date to the end of a file name like this: TheFile.log.2012-02-11 Here is what I have so far: set today = 'date +%Y' mkdir -p The_Logs & find . -name The_Logs ...