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
125 views

Shell script runs differently when schedulled with cron

I have a strange problem with my backup script. To begin with, this is the backup script: ########################################################### # CODE BEGINS HERE ...
2
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3answers
164 views

Bash: issuing trap twice

I have a very simple question. I can't believe the Bash manpage doesn't explain this already, but anyway... If I issue the trap builtin twice [for the same signal], what happens? Is the second ...
0
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2answers
95 views

Why doesn't this pipe command work at this special bash script?

That script test.sh doesn't work after used pipe command. The result shows nothing. Why? #!/bin/bash fun=$( echo $1 ) echo "$fun" commands are as follows, $ echo 1 | ./test.sh
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vote
1answer
54 views

How do I add something to the end of “}” if a pattern is matched?

If I have something that looks like this: hello {sdsdsdsds} pattern {askjdasjkdjasd} hello {siadsd} pattern {iuewer} So if pattern if matched before {*}, I need to add a ;. Output: hello ...
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4answers
2k views

List the number of lines in files

How can I list the number of lines in the files in /group/book/four/word, sorted by the number of lines they contain? "ls -l" command lists them down but does not sort them
1
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1answer
242 views

login/non-login and interactive/non-interactive shells [duplicate]

Are the concepts of login/non-login shells the same as the concepts of non-interactive/interactive shells (respectively)? Or are the concepts orthogonal yielding four different combinations? I am ...
6
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4answers
400 views

what's the difference between using 'single quotes' or not in find command

find ~/ -name *test.txt find ~/ -name '*test.txt' Can anyone help me to construct an example where the first form fails but the second still works. And tell me the difference between them.Thanks!
2
votes
2answers
72 views

How to search empty alternation with tcsh

I want to search some empty alternation with ls but nothing is working. I have a list of files: foo.txt foouubar.txt fooubbar.txt fooubar_1.txt foounix.txt I want to have only foo.txt and ...
2
votes
1answer
77 views

Execute command that was displayed on the screen as a message

A message is displayed many times on the screen after entering certain command. I need to retype the entire suggested command or copy and paste it. Is there a shortcut to do the same using the ...
3
votes
1answer
131 views

Problem with getting interactive input in while read loop

I was doing something like the following minimal example: #! /bin/sh # $1 = file containing list of files to sync # $2 = source dir ; $3 = target dir cat "$1" | while read f do cp -i "$2"/"$f" ...
1
vote
2answers
328 views

Can I hook into the cd command?

I'm trying to set something up on a server I run, when ever I cd into a public_html folder 95% of the time there's a few commands I will always run to check certain things. Is there anyway I can hook ...
2
votes
2answers
336 views

How to create an alias for a sequence of commands? [duplicate]

I know it for one command but how to work with a sequence?
1
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2answers
76 views

how to extract path from file location using shell [duplicate]

how to extract path location from below given string. /opt/oracle/app/oracle/product/12.1.0/bin/tnslsnr expected output. /opt/oracle/app/oracle/product/12.1.0/bin (or) ...
29
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2answers
3k views

How does `cat <> file` work?

cat < file prints the contents of file to stdout. cat > file reads stdin until Ctrl+D is detected and the input text is written to file. cat <> file, at least in my version of Bash, ...
2
votes
2answers
726 views

Update process name in shell, is it possible?

In C/C++ it is in general possible to do strcpy(argv[0], "new process name"). It's a hack used in malicous software to hide real process name. Is such operation possible via shell? What I want to do ...
1
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5answers
1k views

find the max value of column 1 and print respective record from column 2 from file

How to find the max value from the column 1 and echo the respective path location from a file which contains n number of records. $ cat version.log 112030 /opt/oracle/app/oracle/product/11.2.0 ...
1
vote
1answer
516 views

How to keep running a process in Android when disconnecting adb terminal? command “nohup” not found

I'm trying to analyze the reason for random reboots of my phone (see here). Therefore I wanted to record the logcat and kernel messages till the restart to see the logs even after the usb disconnects, ...
2
votes
3answers
201 views

How to parse env variable in a quoted string?

I'm having a hard time getting the value of an environment variable ($GHREPO) in a quoted string. Here is the command I'm running. I'm trying to make a directory with the value of ...
2
votes
1answer
155 views

find and sed (find and replace) causes illegal byte sequence on Mac OS X

I am attempting to perform a find and replace of underscores to dots in a directory for certain filetypes only (.mkv, .mp4, .avi). This is the code that I am using (I'm on Mac OS X 10.9): find . \( ...
108
votes
3answers
7k views

Why not use “which”? What to use then?

When looking for the path to an executable or checking what would happen would you enter a command name in a Unix shell, there's a plethora of different utilities (which, type, command, whence, where, ...
4
votes
2answers
440 views

Using `case` to handle script arguments

Can I use the case statement to handle arguments? So, using -restart I'd like execute "-umount" and "-mount" #!/bin/bash case "$1" in -mount mount /ip/share1 /local/share1 ;; -umount umount ...
6
votes
7answers
744 views

Command line tool to “cat” pairwise expansion of all rows in a file

Suppose I have a file (call it sample.txt) that looks like this: Row1,10 Row2,20 Row3,30 Row4,40 I want to be able to work on a stream from this file that is essentially the pairwise combination of ...
1
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2answers
96 views

Compare and print data from different text files to one in Shell

How can I compare and print data from different text files to one in Shell. I have captures NAS details of three different boxes using SSH, now I need to combine all the three text files to one file ...
1
vote
1answer
938 views

How do I put a time stamp with: wget --output-file=[FILENAME] [URL]

So I've been trying to put a timestamp on some images I'm downloading from a webcam, but so far it's been saving the images with the names camera3_date' here's my line that I enter: wget ...
0
votes
1answer
214 views

check status process output

I wanted to understand how to create a script sh that allows me to see if an additional script functions correctly. For now this is the script that I created. if /run.sh status echo "$SERVICEXE ...
2
votes
3answers
2k views

cshrc execute bashrc within itself?

My school has our Linux accounts using csh/tcsh by default. I, however, have a lot setup on my home bashrc and I'd like to use that at school. BUT there's also some important stuff that happens in our ...
0
votes
1answer
106 views

Trying to debug /etc/init.d/named, no output, replace > /dev/null with /var/log/named.log?

I'm trying to debug named, when I try: [root@test master]# service named start Starting named: [FAILED] it fails silently, so I tried: sed -i ...
18
votes
3answers
9k views

Bash: double equals vs -eq

I am doing integer comparison in bash (trying to see if the user is running as root), and I found two different ways of doing it: Double equals: if [ $UID == 0 ] then fi -eq if [ $UID -eq 0 ] ...
2
votes
2answers
247 views

How to read from a named pipe after the writer process exits?

I want to use named pipes as asynchrnonous task queues (JMS-like, perhaps). For example, suppose a client sends some data that I wish to insert into a database, but I want the client to disconnect ...
3
votes
2answers
4k views

Close all file descriptors in bash

Is there a way to close all the open file descriptors, without having an explicit list of them beforehand?
3
votes
4answers
903 views

How to use sed to selectively remove leading zeros

How can I substitute/remove 0's in this, using sed: 2001:0db8:03cd:0000:0000:ef45:0006:0123 to make it looks like this: 2001:db8:3cd:::ef45:6:123 There are 8 pieces of 4's divided by : in the ...
2
votes
3answers
97 views

Using a command's output to determine the name of the file to redirect output to

I want to run smartctl -a, and use the device serial number from that output as the name of the file to store the output in. I know this can be done by invoking smartctl twice, and slicing up the ...
3
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2answers
2k views

single quote within double quotes and the bash reference manual

In section 3.1.2.3 titled Double Quotes, the bash manual says: Enclosing characters in double quotes (‘"’) preserves the literal value of all characters within the quotes, with the exception ...
13
votes
2answers
900 views

How can variables use “~” for cd'ing?

How can I use a variable - $BASE in my cd. I tried the following but I get an error $ cd ~/z/repo_1_ruby_193/ 23:23:57 durrantm Castle2012 /home/durrantm/z/repo_1_ruby_193 $ BASE="~/z" 23:24:03 ...
2
votes
2answers
119 views

How can I test for a file having a value?

I am using source ~/.rvm/scripts/rvm repos="repo_1_ruby_193 repo_2_ruby_211 repo_3_ruby_191" > rvm_check.txt for repo in $repos do cd ~/zipcar/$repo 2>rvm_check.txt cd .. echo $repo if ...
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2answers
935 views

how to shutdown another computers by using their IPs in shell script [closed]

command to shutdown to collection of servers by IP in specific time by shell script "using ssh command"
1
vote
3answers
243 views

0 byte file created in a simple script

I have a script as below: #!/bin/bash df -k | tr -s " " "," | awk 'BEGIN {FS=","} {print $1,$5}'|sed 1d > file1.txt while read partition percentUsed do if [ $percentUsed > 75 ] then echo ...
1
vote
1answer
169 views

How do you make case statements with ranges

I'm supposed to: Make a case statement that will display the a grade after input. With no loop or conditional. A=90-100, B=80-89, C=70-79, D=60-69, F=0-59 This is what I have so far: ...
2
votes
3answers
542 views

How to create multiple files with different names and different extensions?

I'm trying to create some files that has different names and with different extensions. Let say I want to create for example 3 files with following name and extension: File001.000 File002.001 ...
2
votes
1answer
1k views

Root shell sees pip but sudo pip “command not found”

I have installed python 2.7.8 via make and make install and then pip via get-pip. I have to note that I work behind a proxy which I have set up via http_proxy ftp_proxy https_proxy in my user's ...
2
votes
3answers
547 views

Brackets in if condition: why am I getting syntax errors without whitespace?

I am using the below script to move two days back when script runs at starting two days of the year and also check first and second days of every month and move two days back. if [$month="01"] ...
2
votes
3answers
1k views

Bash File existence test is always true

I have the following lines of bash script to test whether a file exists: MYAPPPATH=$(find $APPDIR -iname myapp* -print) if [ -e $MYAPPPATH ] then echo "File exists" fi However when file ...
11
votes
4answers
7k views

symbolic link to a directory and relative path

I've created symlink with absolute path to the directory (Blink) and have for example following tree: $ ls -l /tmp/A total 0 lrwxrwxrwx 1 root root 6 Apr 3 12:27 Blink -> /tmp/B -rw-r--r-- 1 root ...
6
votes
6answers
2k views

How to clean up file extensions?

I have a directories with .MP3 files which I'd like to change the extensions to .mp3. What's the easiest way to do this? I'm think something along the lines of: find /RootPath -type f -iname "*.mp3" ...
0
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0answers
44 views

od: Put offset n to n of a hexdump to a file in proper hexdump -C (hex+ASCII) format

I have a 155GB canonical hex+ASCII hexdump hexdump -C blah > dump.dp Then ran: strings dump.dp | grep -bo 'XXXX' > found.txt So now, that file contains the string's hex offset in the ...
2
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2answers
53 views

Efficiently copy names in shell

I have noticed an efficient technique that some users use to quickly copy directory and file names in the terminal or shell. The behavior/usage is as follows: Issue ls Click on the desired entry, ...
5
votes
3answers
591 views

How to iterate a zero padded integer in bash?

How does one iterate a string with the form "[A-Z][0-9]*" Or for example: "A000001"? After receiving the variable I split: current_=$(mysql -h"$mysqlhost" -u"$mysqluser" -p"$PASS" "$DBNAME" -se ...
3
votes
1answer
183 views

Run vsim from dmenu — it only works when directly invoked in the terminal

Works: vsim, sh -c vsim Doesn't work: echo "vsim" | sh, echo "vsim" | xargs -I {} sh -c "{}" I want to run ModelSim (vsim) with dmenu, which is triggered using xbindkeys. Details vsim is a ...
2
votes
1answer
6k views

Cant ssh, connection terminates immediately with exit status 254

The most recent thing I remember is changing the soft and hard memlock ulimit to unlimited. Now I cant ssh into the machine. This is the ssh log. Authenticated to IP ([IP]:22). debug1: channel 0: ...
1
vote
1answer
245 views

Sh Script using ftp to put a list of files

So my Script looks something like this: #... files="$(find $line/processed/* 2>/dev/null)" #2>/dev/null used for error output suppression if [[ ! -z "$files" ]] then ...