Questions about shell scripts, executable files that are interpreted by a shell (bash, zsh, etc.).

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3
votes
1answer
139 views

how to deal with arguments when executing a script

how to deal with arguments when executing a script my code is: #!/bin/bash DIR="$1" if [ DIR eq $1 ] then echo -n "total directories:" ; find $DIR -type d | wc -l echo -n "total files:" ; ...
3
votes
3answers
537 views

Processing input line by line (with empty lines) from shell

In a shell script, I need to parse the output of a command line-by-line. The output may include empty lines, and these are relevant. I am using ash, not bash, so cannot resort to process substitution. ...
3
votes
1answer
2k views

bashscript to detect right arrow key being pressed

Why does this always detect as true, even if the keycode is not right-arrow-key? stty_state=`stty -g` stty raw; stty -echo keycode=`dd bs=1 count=1 2>/dev/null` stty "$stty_state" echo $keycode ...
3
votes
3answers
3k views

Script to email all matching files in a directory

Trying to set up a bash script to automate sending data files. Desired end result is to check a specified directory once per week, make a list of all Excel files modified within the last 2 days, and ...
3
votes
3answers
6k views

How to get previous year and previous month in solaris 8

How to get previous year and previous month in solaris 8? I have tried below command but none of them is correct: date +'%m' -d 'last month' date +'%Y' -d 'last year'
3
votes
5answers
531 views

How can I force a script to use more resources?

I'm running a very time-consuming script which takes many hours to end. Watching top I see that it's only taking 5% of the CPU at best, usually around 3%. Is there any way to force the script to use ...
3
votes
2answers
4k views

Remove scientific notation bash script

When I convert MB to GB I'm getting below output. I want this output in normal format. When I use bc I'm getting an error. The text file contains nearly 100 such lines like this. I want to print this ...
3
votes
3answers
3k views

How to convert all .wav files in subdirectories to .aac using neroAacEnc?

I have a collection of music in .wav format, and would like to convert it to .aac/.mp4 using neroAacEnc. How do I do this? I am using Arch Linux x86_64 and Xterm.
3
votes
1answer
3k views

How to move file based on file name expression using shell script?

I want to achieve the following using a shell script. When a script is called with a file as a parameter, it should move the file based on a portion of its name. For example, "Car insurance ...
2
votes
4answers
61 views

move a file that matches a pattern in a shell script

I have very little experience in writing shell scripts and need advice on how I can accomplish the following task. I need to move the most recent file in a directory where the filename matches a ...
2
votes
2answers
70 views

Find and replace all same files between 2 directories

I want to find all files in dir1 having corresponding same file names in dir2, and replace them with the files from dir2. For example: dir1: first.txt second.txt dir2: third.txt first.txt So I ...
2
votes
1answer
92 views

Stable timing for shell scripts?

The run times of scripts vary quite much. I would like to find similar time -function as Matlab's timeit, described here. For instance, I am evaluating these commands here about counting quickly ...
2
votes
2answers
340 views

How do you construct a grep & command to match a number of patterns depending on how many are provided at runtime?

I have exported some MS Word documents to plain text and use this function to parse the contents of the .txt files in the current directory: mo1 () { for i in *.txt; do echo "File: $i" grep ...
2
votes
3answers
4k views

Extracting characters after a particular text

I am extracting a page from website using cURL command. curl "www.google.com" -s | w3m -dump -T text/html > foo.txt The w3m command outputs the HTML page in a much more simpler format so that ...
2
votes
1answer
4k views

“stdin: is not a tty” mails for running scripts as cron jobs

I have several shell scripts (bash) which are started by cron. Every time a script is executed I get an email saying "stdin: is not a tty". Can someone please tell me how to fix this? All scripts run ...
2
votes
1answer
1k views

Linux nuisance: /dev/stdin doesn't work with sockets

Linux has this blitheringly annoying peculiarity that /dev/stdin won't work with sockets - it is hardcoded to return ENXIO. Try this: socat TCP-OPEN:localhost:1234 EXEC:cat\ /dev/stdin,nofork ...
2
votes
3answers
213 views

How can i get five seconds of data appended to the end of file?

suppose if a shell script appends a data to a file.txt like 1........... 2........... 3............. 4............. 5.............. Now i want another script that could check the fresh data ...
2
votes
4answers
8k views

Match multiple regular expressions from a single file using awk

I'm trying to parse a HTML file using shell scripting. There are 4 different regular expressions that i need to catch: name= , age= , class= , marks=. Using grep "name=\|age=\|class=\|marks=" ...
2
votes
2answers
2k views

how to add line in a /etc/sudoers file with the help of shell script (50servers)?

Anyone can help me with shell script, I want to know script which can edit /etc/sudoers file and let me add {{{{{userid ALL=(root) ALL}}}} to 50 server I have on same network?
2
votes
2answers
128 views

how to count number of differences in large streams quickly?

I want to count the number of differences (different bytes) in two large streams (devices/files). E.g. two hard disks, or one hard disk and /dev/zero. The program(s) involved must be fast, as fast ...
2
votes
3answers
1k views

What's the best way to backup files via network on Linux and Solaris machines?

I wonder what the best way to backup files VIA network I have Solaris machines with Oracle 10i with VERITAS cluster, machines are connected to EMC storage /data/oracle directory is mounted on the ...
2
votes
2answers
629 views

Distributing thousands of files over subfolders

I have a folder A with hundreds of thousands of files. I would like to move these files to new subfolders S_i, with, say, 100 files in each (the last folder may have less than 100 files) In other ...
2
votes
2answers
3k views

Concatenate multiple files under subdirectories

My directory structure is given below x:\Project_2012-158A\Sample_4041 SampleSheet.csv 4041_CGTACG_L002_R1_001.fastq 4041_CGTACG_L002_R2_001.fastq 4041_CGTACG_L006_R2_001.fastq ...
1
vote
4answers
113 views

Find and delete all same files (by name) between 2 directories

I want to find all files in dir1 having corresponding same file names in dir2, and delete them from dir1. For example: dir1: first.txt second.txt dir2: third.txt first.txt So I want to remove from ...
1
vote
3answers
85 views

Random sampling and outputting the largest value

I have a fairly large data set ~500 million rows. The data set looks like below. Col 1 is float number, col 2 is mac id(device id) 1616.93,ac:22:0b:a6:22:c3 2872.32,c0:bd:d1:36:bb:49 ...
1
vote
6answers
112 views

How can I pass an environment variable to a script?

Okay, I can display an environmental variable from the commandline: echo $COLUMNS And get a response. But I can't execute that from within a shell script, I get nothing. So, there must be a way to ...
1
vote
6answers
3k views

Print numbers from 1-50

x=1 while [ $x -le 50 ] do echo $x $x=(($x + 1)) done I have wrote the above code. What seems to be a easy task in many programming languages is giving this error for me. solution.sh: line ...
1
vote
2answers
894 views

Command/scripts to check the Reverse DNS Lookup time

I am working on a project in which one master communicates with numbers of slaves. For that it has to make connection with hosts in network. But sometimes it hangs. I think that the reason behind is ...
0
votes
0answers
68 views

!-2 not found when using alias [duplicate]

I'm lazy, so I like to make a LOT of aliases for some of my most common shell commands. I use the command sudo !! quite a bit to tack on sudo for root access, but when I use the following in my ...
0
votes
2answers
77 views

init.d script not working - trying to launch ssh tunnel in background

trying to get a simple file to run at boot. But's not launching. It works if I run it, but, never at launch. This is my init.d script, launch_ssh_daemon.sh: #!/bin/bash ### BEGIN INIT INFO # ...
0
votes
3answers
365 views

How to loop through lines in a file which contains * in each line

I have a file that contains about 800 lines. All the lines contains 1 * character in it. I need to loop through the lines in the file so I used the following simple for loop for i in $(cat ...
0
votes
2answers
5k views

How do run MYSQL scripts from a shell script with bash variables?

Im making a script where I connect to a database, look for a value and then if that value returned something then I will do something else. ip=$("variable is defined here") Then I connect to the ...
0
votes
1answer
818 views

difficalty to save traceroute output in shell variable?

I need to filter and store traceroute output in shell variable (array). But I am getting some unusual output. As I try to explain in following lines. My present directory is temp, having some ...
0
votes
2answers
4k views

Is a shell script is a programming Language [closed]

This is the first question in UNIX: I was started shell script from 2 days before. But I have a conflict: is a shell script a special programming language for a specific shell??
-1
votes
1answer
101 views

Debug an open-source and be confronted with some troubles [closed]

Here is main script . I run it and get some errors like this : ╭─frankwang@ubuntu ~/ion-open-source ╰─➤ ./ionadmin ...
-3
votes
1answer
196 views

SSH with no password

I have a Shell bash file that i run as sudo and it contains a file to send a ssh comand to bulk clients but it asks for the password every time and i do not what key based ssh the password is the same ...
-4
votes
2answers
1k views

“bash: [: : integer expression expected” [closed]

I want this function to return one random word if there aren't any command-line arguments. I am modifying linuxconfig.org's random-word generator to run even when #$ -ne 1. function random-word { ...
21
votes
2answers
851 views

Why escape trivial characters in shell script?

I just opened a legacy shell script (written in old ksh88 on Solaris) and found the following repeated all throughout the code: [ -f $myfile ] && \rm -f $myfile The escaping backslash ...
12
votes
2answers
2k views

Suppress output unless non-zero exit code

What's the best way to suppress output (stdout and stderr) unless the program exits with a non-zero code? I'm thinking: quiet_success() { file=$(mktemp) if ! ( "$@" > "$file" 2>&1 ); ...
11
votes
7answers
4k views

Shortest way to extract last 3 characters of base (minus suffix) filename

I'm trying to set a variable in an sh script to the last 3 characters of the base name of a file (by base name I mean without the path and without the suffix). I've succeeded in doing this but, purely ...
11
votes
2answers
369 views

How to start tailing a file that has not been yet created

I use tail to monitor the progress of jobs that I know will write their progress to disk. Almost always, I know which file they will create before they start running (the jobs are dispatched by a ...
10
votes
2answers
657 views

Having a problem with a shell script counting characters

I'm trying to learn the basics and I have run into an issue with my script counting the characters of a user's input. Here is my script, can someone point out where I'm going wrong please? ...
9
votes
3answers
743 views

how to check the format of a filesystem

I would like to check, in a bash script, on what filesystem type a directory is. The idea is something like if [path] is on a [filesystem] filesystem then filesystem specific command end if
9
votes
2answers
2k views

How to non-invasively test for write access to a file?

In a shell script, how do I easily and non-invasively test for write access to a file without actually attempting to modify the file? I could parse the output of stat, but that seems really complex, ...
8
votes
3answers
455 views

Extract text between three single quotes

I have the following in a file description: ''' This rule forbids throwing string literals or interpolations. While JavaScript (and CoffeeScript by extension) allow any expression to ...
8
votes
0answers
216 views

how to get exit status from the command before the last [duplicate]

I have solaris machine ( solaris 10 ) please Look on the following simple commands (haconf -makerw | grep -iq "Cluster already writable") # haconf -makerw VCS WARNING V-16-1-10364 Cluster ...
8
votes
2answers
2k views

Find all files with a Python Shebang

I'm trying to run a PEP8 check against a large source tree. The tree is comprised of a mix of files in various languages. The idea is to check all the Python scripts without having to explicitly list ...
7
votes
5answers
612 views

List out strings which are substrings of other strings in the list

I have a list of names like so: dog_bone dog_collar dragon cool_dragon lion lion_trainer dog I need to extract out names that appear in other names like so: dragon lion dog I looked through the ...
7
votes
1answer
5k views

How to strip color codes out of stdout and pipe to file and stdout

I have a program that uses printf with some tput mixed in it and I'd like to pipe the output to stdout as well as a file. I'd prefer to use sed since I don't want any unnecessary dependencies on my ...
6
votes
3answers
526 views

Weird float rounding behavior with printf

I've read some answers on this site and found the printf rounding desirable. However when I used it in practice, a subtle bug led me to the following behavior: $ echo 197.5 | xargs printf '%.0f' 198 ...