4
votes
4answers
270 views

extract every nth character from a string

I am trying to figure out a solution for this question. My approach to this problem so far is as below. Append all the characters together to make it a long string. After the above step, remove ...
6
votes
5answers
254 views

Number of characters in a shell command's output

I am writing a script which needs to calculate the number of characters in a command's output in a single step. For example, using the command readlink -f /etc/fstab should return 10 because the ...
4
votes
1answer
62 views

Length of argument inside a function of an sh script

I have a FreeBSD 9.3 RELEASE server and I am trying to write a shell script using sh. I am trying to get the length of a variable that is passed to a function in a shell script, like so: #!/bin/sh ...
4
votes
2answers
96 views

Write variable containing large text with \n to a file with common shell interpreters. How do you do it?

Environment: linux shell or better, ash shell in busybox (example system: Openwrt). Given a string variable with large text "${a}" constructed in this way: for index in $(seq 1 40000); do #it is ...
9
votes
6answers
2k views

How can I test if a variable is empty or contains only spaces?

The following bash syntax verifies if param isn't empty: [[ ! -z $param ]] For example: param="" [[ ! -z $param ]] && echo "I am not zero" No output and its fine. But when param ...
0
votes
3answers
92 views

grep substring between quotes

Let's say I have a string like this: title="2010-09-11 11:22:45Z" How can I grep the date itself and disregard the quotes/title/Z? The file can contain more strings like: randomstring ...
4
votes
4answers
148 views

Check if content of file has length X and contains only specific characters

Let's say, I have files that contain only one docker id: myid.id: 28fe2baadbe8da32ed0b99c69b11c01b2d141bc5b732b81e0960086de52fc891 I want to check if the content of my.id is exactly 64 characters ...
4
votes
5answers
151 views

Add leading characters infront of string using printf or echo

How can I add leading characters to fill a string to a certain length? Assume I want to add zeroes infront of a string, if said string is shorter than 20 characters: printf '%020s\n' "$line" ...
0
votes
1answer
45 views

Must pass urls in quotes

I'm trying pass a URL to mpv for it to play it as a network stream. This can be done in bash with the following syntax: $ mpv http://myvideosite.com However, zsh wants to evaluate the URL as ...
1
vote
1answer
64 views

Verify the length of a variable

I've to verify the length of variable read (my script limit to five the characters inserted), I think about something like this: #!/bin/bash read string check=${#string} echo $check if [ $check -ge 5 ...
5
votes
1answer
182 views

Test -n gives unexpected result

I understand test -n <expression> to return false if the expression evaluates to a string length of greater than 0. Why then does the following happen? Macbook:~ echo ${#undeclared_variable} 0 ...
1
vote
3answers
601 views

How to get a string between two special characters using Shell?

I want to get a string between two special characters. For example, /home/oracle/ggs/text.ext I want oracle/ggs in the above string. How can I do this using bash?
4
votes
3answers
2k views

Case-insensitive substring search in a shell script [closed]

I'm trying to create a script which runs a command and compares the output of that command to a certain string to see if it contains that substring, ignoring the case of the string needed to be ...
2
votes
5answers
7k views

Extract date from a variable in a different format

Let me explain you the problem $ date +%c -d "$d" Tue 31 Dec 2013 01:13:06 PM CET $ date +'Today is %F' -d "$d" Today is 2013-12-31 This solution corresponds to current date. But I have one ...
0
votes
0answers
15 views

UNIX: How to extract date from a variable storing a UNIX DATE [duplicate]

I am facing following issue: Input: F=`date +%Y%m%d` echo $F Output: F=20131231 But when trying this(File Name:A.sh): C=`date` G=`$C +%Y%m%d` echo $C echo $G Output: A.sh[6]: Tue: not ...
0
votes
1answer
364 views

Test variable if its string or not

I'm writing a script which will have some arguments and so I am using getopts but i want to solve the problem with one argument. I use a switch, for example -d, and I want the argument for -d will ...
2
votes
4answers
751 views

Can awk use field identifiers also for shell strings (variables)?

Well, this apparently is not possible the way I'm trying it. This alternate approach to obtain bar as a resulting string works, though: #!/bin/bash path1=/usr/tmp/foo/bar/baz awk -F/ '{print $5}' ...
4
votes
2answers
552 views

Convert MAC address to Link-local address with bash

How can I convert a Mac address into an ipv6 Link-Local address? you have to add fe80:: at the start and insert ff:fe in the middle furthermore all leading zeros must be stripped
2
votes
1answer
250 views

shell parameter substitution to rename files

I need to rename filenames which starts with "foo" into "boo" This is the script I used #!/bin/sh for f in *.jpg; do mv -- "{$f}" "${f/foo/boo}"; done but when i run I get a bad substitution ...
2
votes
2answers
2k views

Testing a string containing only spaces (tabs, or “ ”)?

My code below doesn't work: stringZ=" " if [[ "$stringZ" == ^[[:blank:]][[:blank:]]*$ ]];then echo string is blank else echo string is not blank fi Result: string is not blank # wrong ...
0
votes
3answers
372 views

Extract the base file name from a URL

url=http://www.foo.bar/file.ext; echo ${url##/*} I expected this code to print file.ext, but it prints the whole URL. Why? How can I extract the file name?
1
vote
2answers
2k views

How to correctly concatenate strings in shells script?

I have a bash shell which I need to modify, and I have to set a variable in a script and then call another script. My variable, EXTRA_JAVA_OPTIONS must be -javaagent:myagent.jar="-d 0 -i 1000 -l log2 ...
6
votes
3answers
3k views

How to defer variable expansion

I was wanting to initialize some strings at the top of my script with variables that have no yet been set, such as: str1='I went to ${PLACE} and saw ${EVENT}' str2='If you do ${ACTION} you will ...
2
votes
3answers
589 views

Find word in sentence with Bourne Shell (sh)

I'm trying to determine if a particular word appears in a sentence using Bourne Shell (sh). For example: #!/bin/bash INPUT='Lorem ipsum dolor sit amet.' if [[ "$INPUT" == *dolor* ]] then echo ...
2
votes
4answers
602 views

Stripping all vowels but the first from a set of strings

I have a string comprised of multiple substrings, separated by underscores. For example: AbcdAEfd_hEgdgE_AbAAAAA. I need to remove all vowels except the first from each substring. So: AbcdAEfd -> ...
3
votes
2answers
468 views

Change string occurrences in file while respecting DOS new line sequences

I use Visual Studio for my C# development while using Cygwin for some of the tasks that require scripting. Recently I wanted to change all occurrences of string AAA to BBB in my project's files. I ...
3
votes
3answers
995 views

Extracting text from a text file in bash

I have a large text file that is all one line. In the text are several sections that looks like foo=12345 and I need to extract them all as separate lines, ignoring the rest of the file. For ...
8
votes
3answers
9k views

Bash - test for newline?

In various places around the web I've found: \015 \012 \x0a - hex \n \r all as synonyms for various newlines / carriage returns... But in this small script I cannot recognise when I come across a ...
2
votes
4answers
307 views

Generate lists of page numbers for 2-up duplex printing: 2,3,… and 1,4,…

How can I generate the following increments? 2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31,34,35,38,39,42,43,46,47,...,135 and ...
7
votes
7answers
2k views

Bash - Continuous String Manipulation

#!/bin/bash FILE="$(basename "$1")" FILE="${FILE/%.jpeg/.jpg}" Is there anyway to glue these two lines together into a one-liner?
2
votes
3answers
3k views

Bash string replace multiple chars with one

I'm replacing, from a feed title, all chars except letters and digits with a dash to use the result as a safe filename for any filesystem: $ t="Episodie 06: No hope of riding home (NEW) - Advanced ...
1
vote
1answer
253 views

Check a bash variable against a file

I have a bash variable ($HTTP_COOKIE) which contains a string. I want to check if this string matches the content of a given file (token). I'm working on a busybox linux. How should I do?
2
votes
3answers
148 views

expr help - managing strings

I need to take text like this: A234321=http://www.google..... a normal URL And pull out only the URL, getting rid of the first part. I think I can use expr to do it, but I can't figure out the ...
2
votes
3answers
1k views

Is there a tr for translating into longer strings?

tr is great for translating a set of characters to another set of characters. Sometimes, I want to translate a set of characters to a set of strings, e.g. all < and > to &lt; and &gt;. ...
7
votes
7answers
5k views

How to check if $PWD is a subdirectory of a given path

E.g. check if $PWD is a subdirectory of /home. In other words I'm searching for a bash string operation to check if one string starts with another.