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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2
votes
0answers
39 views

How to get the mplayer's single-line playing progress info?

mplayer shows and refreshes a single-line playing progress when playing a media file. A sample result is: A: 17.2 (17.2) of 213.0 (03:33.0) 0.5% And I'm trying to grep this playing progress and ...
1
vote
3answers
124 views

How do I make an output for grep fail?

I am using if-else statement to search for keywords and displaying the results in the terminal, here's an example of my code. read finding if ["$finding" != "" ]; then grep $finding ...
2
votes
1answer
34 views

Export path with space in directory name [duplicate]

I have a path "/third/party/city of las vegas" when cd the path I use "/third/party/city of las vegas". In .profile file I have exported the path to a variable as follows export ...
1
vote
2answers
63 views

readlink -f not working on multiple files

I tried to run readlink -f on multiple files by using wildcard "*", but it evaluates other files as operand Command readlink -f *log Output (desired) /home/trail_1.log /home/trail_2.log Am I ...
13
votes
6answers
1k views

Is there another simple way to append line to end of file other than `>>`?

Recently I'm echoing short sentences to a tree_hole file. I was using echo 'something' >> tree_hole to do this job. But I was always worried of what if I mis-input of > instead of >>, ...
0
votes
1answer
36 views

How to autoremove with apt?

After uninstalling a package I used to do apt-get autoremove to remove other unused dependencies. I understand that apt (rather than apt-get) is the modern way to manage packages on the command-line ...
1
vote
2answers
410 views

Can I put more than 1 condition in if?

Is it possible to put more than 1 condition in an if statement? if [ "$name" != "$blank" && "$age" == "$blank" ]; then Is it possible? If not how am I supposed to do that?
5
votes
3answers
235 views

Save exit code for later

So I have a little script for running some tests. javac *.java && java -ea Test rm -f *.class Now the problem with this is that when I run the script ./test, it will return a success exit ...
2
votes
2answers
97 views

How to use variables inside single quotes

I have an application which takes as an input attributes in double quotes embedded in single quotes. Take for example this right command: command -p 'cluster="cl1"' In order to automate it, I ...
3
votes
2answers
86 views

How to use tee to capture STDOUT from a code block to a filename defined within the block?

I want to send STDOUT for a script block to a file which name is defined by a variable within the block. However, when I use tee, it seems the variable outside the block doesn't exist anymore. Without ...
2
votes
0answers
56 views

Is there a difference between double quoting a variable or a whole line in echo

When you type, for example, echo Variable "$var" is not initialised. and echo "Variable $var is not initialised." the front end result is the exact same (as far as I know, at least). But I was ...
1
vote
1answer
54 views

rsync recursively with a certain depth of subfolders

I want to rsync a folder recursively but want subfolders included only to a certain depth. For example I would want a depth of 1,2,3 or 4 subfolders like this: source/ ├── subfolder 1 │   ├── ...
2
votes
2answers
124 views

Move specific files from multiple directories

I have got tons of directories with thousands files of various filetypes: dir |__ subdir | |__ file.foo | |__ file.bar | |__ file.txt | |__ (...) |__ (...) What is fast and ...
0
votes
1answer
19 views

Is field splitting and filename expansion turn off in RHS of variable assignment portable?

In most POSIX compliant shell like bash. ksh, dash, mksh, pdksh, when variable assignment occur, field splitting and filename expansion (and brace expansion if the shell supports) are not performed in ...
0
votes
1answer
73 views

How do I put a checksum in a script?

I was (am) having trouble installing Eagle on my Linux (debian 8 jessie) computer. I was reading the installer script, when i noticed there is a checksum for the install script in the install script? ...
1
vote
1answer
27 views

How do I transfer files over ssh and also change their permission on the remote server without having to log in twice

guy@home~% scp file.* guy@server.server.com:/users/guy/public_html/kool-stuff/ Ok so this transfers some files. Then I usually have to login in another terminal and do this in order to make them ...
0
votes
2answers
51 views

Whats wrong with this case statement?

UPDATED: I am trying to do some color changes with my keyboard using apexctl depending on what time it is. But my case statement is giving me trouble. I want to compare the time when the script runs, ...
3
votes
1answer
59 views

What's the shortest way to find my WAN IP address at the command line? [duplicate]

What's the shortest command I could use to find out my WAN IP?
0
votes
1answer
26 views

How do i create a function to test if the input contains any character? [duplicate]

I have this set of example here to test if the user has keyed in any data after he presses enter. echo -n "Type a digit or a letter > " read character blank="" if [ "$character" != "$blank"]; ...
1
vote
2answers
63 views

Makefile make install not executing multiple line commands

I have a Makefile that contains an install section to allow me to make install after building the source code. The install section contains two lines of shell commands: install: /usr/local/lib cp ...
2
votes
3answers
26 views

Can RSH be told to use a specific shell

I am working with a c++ application which fires off a system command that launches a RSH sequence such as: rsh MACHINE \"setenv DISPLAY machine:0;setenv TESTVALUE1 'test';setenv scenTime 0;setenv ...
2
votes
3answers
126 views

Variable expansion in Bash

I tried the following commands variable='one|name' echo $variable The output is one|name whereas echo one|name gives an error No command 'name' found. This is reasonable because bash treats | as ...
0
votes
0answers
12 views

PBS limiting the number of process on a node

I am trying to run a program on cluster. The program can distribute each of the calculation with an corresponding parameter, say k1, k2,...k4, to run on one core. I want to use 4 nodes with 1 ...
6
votes
2answers
926 views

What does `date 2&>$0` do?

I am looking at a co-workers shell code and I saw this: date 2&>$0 I know what date does, but what's 2&>$0 doing? He's out for a while, so I can't ask him what this part was about.
2
votes
2answers
89 views

Filtering a file on a string

I have a file which looks like this a 0 gene1 56 0 6S32M12S * b 256 gene2 56 0 6S32M12S * c 256 gene3 55 0 6S27M17S * d 16 gene4 110 9 19S25M6S * e 272 ...
1
vote
1answer
39 views

How does executing a file change the std input?

Imagine I have a script, which contains the goto command. The goto command will search in the std input for a line like this : jumpHere. But the std input is by default the terminal. It only makes ...
7
votes
2answers
867 views

Was there a '\0' at the end of every script?

I'm wondering how did you dertermine the end of a script/file? I'm especially interested for old Unix versions (like V6). Is there a '\0' after the last written character?
3
votes
2answers
72 views

terminal warn on close when opened within a script

First, the question: How can I warn the user that a script is running when the user clicks the close button and the terminal itself (and the process running in it) was started from the command line. ...
2
votes
2answers
44 views

Changing variables in a forked process from outside that fork?

In theory with this block, you should only see "running..." once(or less), but in practice, it repeats until it's manually killed. How do I change the value of x inside the forked process to false ...
1
vote
0answers
26 views

optimisation of bash globs

Looking for a guide to optimising regexp matches in bash. I have a script that loops over a very long list of URLs looking for patterns. Currently it looks a little like the fragment below. Is there ...
0
votes
0answers
9 views

trying to run a windows program with Crossover on my mac

I installed the program through wine and it made a bottle for the windows program. When I try to launch it I get the following error: "The COM library could not be initialized." Please help? What ...
2
votes
1answer
86 views

Avoid backslash expansion with echo in dash

First create a file with this exact content: a\nb I named this file foo, if I run the following, it prints the exact content of the file: bash -c 'bar=$(cat foo);echo "$bar"' But if you run it ...
-2
votes
3answers
67 views

Why do I get “integer expression required”?

I'm trying to have a small function that I then call. To keep it simple I just want to validate that 12 is divisible by 2,3 and 4 The code is: divisible_by () { under_test=12 from=2 to=4 ...
1
vote
3answers
131 views

How could I reach root after switching from bash to zsh?

It's very weird that after switching to zsh from bash, I can't access root. I normally use 'su' to login as root after I login as a normal user (username is normalusername) with less privileges. And ...
2
votes
2answers
150 views

output both stderr and stdout on console and store them in a file at same time

may I output both stdout and stderr on console screen and store one of them into a log file? I write a test shell script: #!/bin/sh echo OUT! >&1 echo ERR! >&2 I can output both of ...
3
votes
2answers
46 views

Test if valid executable

Is there a (relatively) simple way to test if an executable not only exists, but is valid? By valid, I mean that an x86_64 Mach-O (OS X) executable will not run on an ARM Raspberry Pi. However, ...
2
votes
1answer
76 views

Behaviour of 1>&0 in bash

So I am trying to learn more about file descriptors and their redirections. At the moment I am exploring an edge case of doing 1>&0 and I cannot quite understand what is happening there. $ ...
34
votes
2answers
4k views

Why is using && 75 times faster than if…fi and how to make code clearer

I have the following working code: largest_prime=1 for number_under_test in {1..100} do is_prime=true factors='' for ((divider = 2; divider < number_under_test-1; divider++)); do ...
0
votes
0answers
78 views

PHP “Output file write error” with shell_exec and stdin (|)

php -a echo shell_exec('djpeg image.jpg | pamfile'); result: Output file write error --- out of disk space? stdin: PPM raw, 500 by 373 maxval 255 (djpeg converts a jpeg to PPM and writes to ...
0
votes
1answer
43 views

How i make this script execute every minute without cron? [duplicate]

I have this: #!/bin/bash wlan=`/sbin/ifconfig wlan0 | grep inet\ addr | wc -l` if [ $wlan -eq 0 ]; then echo wlan0 not connected, connecting... echo sudo ifup wlan0 logger wlan0 reconnected. echo ...
5
votes
0answers
60 views

HURD: Why is remote process not killed?

On most UNIX systems this will not leave a process running: ssh example.net sleep 1000 <<CTRL-C>> I have tested this behaviour on aix centos debian dragonfly freebsd hpux irix mandriva ...
95
votes
7answers
11k views

How to kill a runaway cat?

Many times I accidentally run the cat command on files have contents up to few thousand lines. I try to kill the cat command with Ctrl+ C or Ctrl+Z, but both only take effect after the total output ...
4
votes
3answers
159 views

Using | pipe character from a $variable makes it treat as just another argument in bash; how to escape it?

I have a bash script like this export pipedargument="| sort -n" ls $pipedargument But it gives the error ls: |: No such file or directory ls: sort: No such file or directory It seems to be ...
0
votes
1answer
51 views

From Mysql query output to retrieve files in the file system and rename the files

I have to call a SQL query from bash that outputs 1000 rows of two columns File_Path (Eg., /opt/files/dest/2.bin) Name_of_the_file (Eg., fax attachment.pdf, invoice.docx... yes, there are spaces). ...
2
votes
2answers
94 views

Feed source command with a pipe

Previously I used source command like this: source file_name But what I'm trying to do is this: echo something | source Which doesn't work.
3
votes
1answer
79 views

GUI terminals(?) reset $SHELL

I've been playing around with the fish shell for a few days and I like it. In order to start fish in a terminal via a quicklauncher or menu, I'm using a script like this:1 #!/bin/sh export ...
1
vote
1answer
37 views

Remotely connect to computer when connection partly fails

I have a Debian computer acting as a server at home. It has a dovecot+postfix mail server, an SSH server, an apache server, and everything you would expect from a do-everything server. At home, it is ...
1
vote
3answers
92 views

Compare two files and print unmatched lines [duplicate]

I have two files with the below data; I need the difference between two files. I tried with diff but it also shows line which are common in the two files: (22372 Dec 4 15:36 ...
0
votes
2answers
62 views

Combining two bash script and using a menu

I have two scripts, one that is used on a folder with csv files and another on a folder with .tar.gz files. In the second script, I first unzip the files before doing anything with them. Now I want to ...
0
votes
1answer
92 views

linux/shell command to control screen brightness in android

I am working on a kiosk project using an android tablet.If there is no input power to the kiosk for a long time then, the tablet will eventually shutdown.In order to auto-reboot the tab when the power ...