Questions tagged [syntax]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
1 answer
47 views

Is there a way to make a comment after a "\" has been used to split a shell command onto differemt lines? [duplicate]

I am using arch and bash. Everything is up to date. I have this command which works just fine yad \ --timeout=2 \ --undecorated \ --posx=1200 --posy=633 \ --title=" " \ --window-icon='/home/$...
Kes's user avatar
  • 799
-2 votes
2 answers
54 views

Why is double bracket used to 'ensure' some commands, since it is not a logical check for "does it exist or not' (false/true)?

Recently I've been trying to figure out more and more shell syntax and logic behind some lines within scripts and I have the following question: What is the purpose of [[expression]] in the example ...
Andreyan Enchev Boyadzhiev's user avatar
4 votes
2 answers
80 views

How to make the (N) patterns of the zsh eatable by bash?

I am trying to develop a script which runs (and, ideally, does the same :-) ) in zsh and Bash. Problem is, that at a point, the zsh-specific part contains a pattern ending with (N). So: this_pattern*(...
peterh's user avatar
  • 9,541
0 votes
2 answers
159 views

Syntax error: "(" unexpected (expecting "fi") when using calculations

I am relatively new to shell, and I am getting a syntax error where I am still confused. #!/bin/dash ls="ls -l test" small=0 medium=0 large=0 for i in $(seq 11 9 56) do filename=$(echo ...
user avatar
0 votes
1 answer
55 views

Comments are causing errors after changing the value of "histchars" in zsh

Why, after using set histchars='?', is there an error that occurs every time I source ~/.zshrc? /home/user/.zshrc:1: bad pattern: # In other words, every # token within comments is causing some ...
user avatar
-3 votes
1 answer
75 views

What's "[@]" doing to variable in bash for loop

I was looking at how Gentoo's ebuilds are made and I found the following code: _VIM_PLUGIN_ALLOWED_DIRS=( after autoload colors compiler doc ftdetect ftplugin indent keymap macros plugin spell ...
Peter Petigru's user avatar
0 votes
1 answer
208 views

What does "*", "**", and "***" mean in Timeshift filters?

When excluding a folder, Timeshift generates a filter rule of this format: /home/nils/.cache/*** What do the three stars mean? And what do two or a single star mean?
Nils Lindemann's user avatar
-1 votes
1 answer
46 views

What is "in" in Bash?

I have encountered this in the syntax for case after calling help case and getting case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac. There was a question, whether "in" is a bash ...
Juandev's user avatar
5 votes
3 answers
937 views

What does \ mean in bash and find?

I know that \ is an escape character, but when I write \ in bash, I have something like this: System-Product-Name:~$ \ > So bash waits for some instructions? When I use System-Product-Name:~$ \ &...
Marcus's user avatar
  • 241
-1 votes
1 answer
60 views

What are * and / in Bash?

I was trying to understand the following code ls -d */ and came to the explanation that */ "matches all of the subdirectories in the current directory". But that answer points out, what this ...
Juandev's user avatar
0 votes
0 answers
124 views

How does the nftables set-syntax replacement for meters work exactly?

nftables nowadays recommends to use sets instead of meters when e.g. creating dynamic per-IP blacklists (example adapted from man pages v0.98: set blackhole { type ipv4_addr flags dynamic ...
reijerh's user avatar
0 votes
2 answers
115 views

Dangers of executable file with '#' in name?

This might be a FAQ--happy to have the question closed if it's a dupe--but I'm not sure how to find it if so. I'd also be happy with an answer that simply told me how to find the relevant ...
Mars's user avatar
  • 103
0 votes
2 answers
108 views

what does syntax .= means in perl

I came across a Perl script which uses following .= syntax $key .= $descriptions[$i]; what does .= means here
Worker's user avatar
  • 37
0 votes
2 answers
412 views

How to search for a pattern with sed and replace another substring on that line

I need to find all lines in my data file that contain NO_ID and then replace the string "confirmed" by "to be confirmed". I tried this: sed '/NO_ID/, s/confirmed/to be confirmed/' ...
elmo's user avatar
  • 105
12 votes
2 answers
8k views

What does command eval "$(/opt/homebrew/bin/brew shellenv)" actually do?

Homebrew requires us to add eval $(/opt/homebrew/bin/brew shellenv) to ~/.zprofile. What does this actually evaluate to and what does this accomplish? I am a bit new to shell scripting. I know $var is ...
Osbridge's user avatar
  • 123
0 votes
1 answer
53 views

Confused about java -version [duplicate]

For every program/utility on Unix, I would type the name of the program followed by --version to check its version, like so program --version If I understand correctly, the double dash -- is used to ...
user avatar
1 vote
0 answers
29 views

Disk usage command not producing expected number of outputs [duplicate]

I want to run disk usage command (du) on both a parent directory (to find the total of all its contents), and then additionally on one of its subdirectories only. If I try to pass multiple paths into ...
teeeeee's user avatar
  • 187
0 votes
0 answers
191 views

converting /etc/network/interfaces network config syntax to netplan

Trying to do some network configuration after upgrading to Ubuntu 22.04 (from 16.04) and am a bit confused with the syntax.. I'm a total noob! I've googled a lot but still not able to find what I'm ...
Alex's user avatar
  • 1
-1 votes
2 answers
159 views

Test for a number in bash [duplicate]

Is this the correct way to test for a number, with double [[]] enclosing :digit: and single quotes surrounding the regex ? if [[ "$var" =~ '^[[:digit:]]+$' ]]; then
Vera's user avatar
  • 1,183
0 votes
1 answer
34 views

Compact form of a bash file extension test condition

I am testing whether arguments are not video files (.mp4, .mkv). Can I clean this so as to make it more compact test. if [[ ! "$1" == *.mp4 || ! "$1" == *.mkv ]]; then
Vera's user avatar
  • 1,183
0 votes
1 answer
683 views

Bash script error: syntax error near unexpected token `('

I want to run a command a number of times but with different arguments passed to it, so I wrote the following shell script to do that #!/bin/bash ...
coopdog218's user avatar
9 votes
1 answer
491 views

/RE/ vs. "RE" in awk

In awk, the first argument to the sub() and gsub() functions, the second argument to the match() function, and the optional third argument to split(), is an extended regular expression. Such an ...
Kusalananda's user avatar
  • 323k
0 votes
0 answers
27 views

Difference between command1; command2 and (command1; command2) [duplicate]

I know that command 1; command 2 means that: run command1 first, then run command2. But, what if the command has parenthesis around it ? like (command1; command2). What is the difference between these ...
Hanah's user avatar
  • 1
1 vote
0 answers
50 views

How should alias in command substitution behave?

I tested a few scripts with different shells, and the results differ. # test 1 foo(){ echo $(al);} alias al='echo 123' foo # test 2 alias al='echo 123' foo(){ echo $(al);} alias al='echo abc' foo # ...
anonymous's user avatar
1 vote
1 answer
72 views

bash `if` block contents fail to execute due to syntax error on extended glob pattern in MacOS

Short Version: When extended glob is turned on inside a bash if block on my Mac, the entire block fails with a syntax error on any extend glob pattern contained in the block, even if it follows the ...
Arcticstar's user avatar
0 votes
2 answers
69 views

bash scripts - need help with syntax

I am reading the last line of 4 different files and grep for a certain string. Based on the string, I need to rename the source file. All 4 files have a different grep string and eventual target name. ...
Gail A. Jones's user avatar
0 votes
0 answers
29 views

Correct if statement syntax in shell script [duplicate]

Following codes echo 'input text : ' read -a names for((i=0;i<${#names[@]};i++)) do name="${names[$i]}" echo "given input is" echo ${name} test="test1" ...
Guldam Kwak's user avatar
0 votes
2 answers
74 views

Unable to uncomment just the cron by matching the string MYAPP

Below is my existing cron which i wish to enable crontab -l ####Cron to auto restart MYAPP ###*/15 * * * * ansible-playbook /web/playbooks/detectMYAPP/va_action.yml | tee -a /web/playbooks/...
Ashar's user avatar
  • 459
1 vote
2 answers
108 views

how to print PID along with the process dump

I wish to combine both the below commands: ps -ef| grep -v grep|grep java | awk ' {print "PID is:" $2}'; PID is:515 PID is:22145 PID is:32703 ps -ef| grep -v grep|grep java wladmin 515 ...
Ashar's user avatar
  • 459
1 vote
1 answer
180 views

test returns wrong value (but no errors) depending on the presence of spaces around the operator

If there are spaces around the operator, test returns the correct value of the expression. But if there are no spaces, it doesn't throw any syntax error and always return true. $ test "A" == ...
robertspierre's user avatar
0 votes
0 answers
87 views

How to grep from a variable

I'm trying to grep from a variable, I'm not sure why the logic isn't working correctly. I would like to enter the loop when the counter is 1 and then check the sta_status variable if the expression ...
Nir's user avatar
  • 1
0 votes
0 answers
17 views

How is the syntax with a loader before the command desribed in bash and other similar shells? [duplicate]

While reading this I saw this kind of strange command $ /lib64/ld-linux-x86-64.so.2 ./app $ LD_DEBUG=all /lib64/ld-linux-x86-64.so.2 ./app Unexpectedly they really works What are these? The man pages ...
phuclv's user avatar
  • 2,010
13 votes
4 answers
985 views

Empty variable is treated as logical "true" with `$var && action` (shell parsing)

Consider a simple debugging style where $debug would be set either to true or false according to some command-line flag: $debug && echo "Something strange just happened" >&2 ...
roaima's user avatar
  • 108k
0 votes
1 answer
63 views

Curious syntax error in script

I am creating a bash script to get cpu%, pps & incoming kbps #!/bin/bash INTERVAL="0.5" # update interval in seconds IFS="enp0s3" while true do # Read /proc/stat ...
ph3ro's user avatar
  • 378
0 votes
2 answers
70 views

Getting an error in the if condition

I am just checking whether the password contains a small and capital case letter, I am getting an error at line 19. myscript.sh: #!bin/sh read password conditionarr=(0 0) if [[ $password =~ [A-Z] ]] ...
bigstreet's user avatar
0 votes
0 answers
512 views

x unbound variable

I am trying to run that script here: #!/bin/bash set -o errexit # be strong with errors set -o nounset # be strong with unset vars PROG="${0##/}" # Scriptname USAGE="usage: $PROG ...
uek1967's user avatar
-2 votes
1 answer
183 views

Issue with grep pipeline in conditional

I'm a noob with bash scripting I'm trying to learn but I don't know how to fix this: ./elleviemme.sh: line 7: unexpected token `|', conditional binary operator expected ./elleviemme.sh: line 7: syntax ...
hflnmlie4594's user avatar
0 votes
1 answer
119 views

What does backticks do when in beginning of line in a bash script

I have noticed a weird behavior when a backtick is used in the beginning of line in bash scripts. example 1: echo "Test" `ls` Output: Test and ls is ignored. example 2: `test ':";`|)...
user7864052's user avatar
0 votes
1 answer
303 views

Syntax in conditional expression comparing with regex

I have tried to execute the code below on my Ubuntu machine, but it keeps saying "syntax error in conditional expression" and "syntax error near '0-9'" can you tell me why? while ! ...
user528910's user avatar
0 votes
1 answer
158 views

vconsole setup: unable to open the include file euro2

I formatted my Arch Linux and reinstalled for some reasons I wanted to start over After installation, a very strange error appeared. In the chrooted installation I created the file /etc/vconsole.conf ...
Devilas's user avatar
  • 77
0 votes
1 answer
886 views

alias in ash - limitation, syntax issue?

I'm running OpenWRT in a NAS (WD-MBL) and putting together a set of aliases to make maintenance easier via the command line. These work as expected: alias shutdown='sync && wait && ...
Groucho's user avatar
  • 31
3 votes
1 answer
264 views

tmux configuration: command output substitution doesn't

I am trying to make parts of my .tmux.conf file conditional depending on the kind of system I'm on. For a start, I want one part to only be processed on MacOS. The man page says that I can use the #(...
q.undertow's user avatar
-6 votes
1 answer
69 views

Is there an example for a shell or computing accessibility culture aspiring a shell with more special characters and if so what is it? [closed]

I was always a bit frustrated from the lack of characters in modern computer systems such as, from what I know: A global template literal character for which the closest character today is a backtick ...
Lahor's user avatar
  • 113
0 votes
1 answer
881 views

How do I append the outputs of the echo -e command into two separate files, simultaneously?

First, Thank you for your time and effort to help me with this situation. Now, without further ado, my issue. I am a student in Cybersecurity and I am attempting to make bash script to enumerate my ...
James Smith's user avatar
-1 votes
2 answers
58 views

averaging a column of a file

I have a CSV file (with time-stamped data), and I have a script that will break each month of the year into a separate file.  The script will take that month and average out the data to a single value....
stormctr2's user avatar
-2 votes
2 answers
157 views

bash error syntax random number [closed]

My assignement is to show a random number (od -vAn -N4 -tu4 < /dev/urandom) between two numbers in read. I don't understand why there are syntax error when I check the min value exception and with ...
Nicolas Pellerin's user avatar
0 votes
1 answer
154 views

linux shell script with if and shopt [duplicate]

I've written the following shell script: #!/bin/bash ... #delete downloaded file if [ "$param" == "delete" ]; then shopt -s extglob cd $DataPersistent/download/ rm -f ...
laogao's user avatar
  • 11
-2 votes
1 answer
283 views

In the synopsis of a man page, what do ellipses following brackets mean? [duplicate]

The following image is from the POSIX documentation's section on Utility Argument Syntax. My question is this: Are the two argument forms in the image more or less identical, besides one using the ...
Nicholas Cousar's user avatar
0 votes
0 answers
272 views

tcpdump to monitor snmp from subnet causing syntax error

I'm trying to monitor SNMP from 2 hosts on the same subnet; 10.52.17.31 and 10.52.17.32. They are on the only machines on that subnet. Using the following commands I receive a syntax error: tcpdump -...
Frank's user avatar
  • 129
1 vote
1 answer
444 views

Hyphen in bash function names [duplicate]

Am writing bash functions. It looks like function names can include hyphen: -. Thus indus-headrc () and indus-tailrc (). Had thought that only underscore is allowed.
Pietru's user avatar
  • 371