Linked Questions
114 questions linked to/from Understanding "IFS= read -r line"
287
votes
5
answers
79k
views
Why is using a shell loop to process text considered bad practice?
Is using a while loop to process text generally considered bad practice in POSIX shells?
As Stéphane Chazelas pointed out, some of the reasons for not using shell loop are conceptual, reliability, ...
- 158k
132
votes
6
answers
62k
views
Why is setting a variable before a command legal in bash?
I've just encountered several answers such as to parsing a delimited text file... that use the construct:
while IFS=, read xx yy zz;do
echo $xx $yy $zz
done < input_file
where the IFS variable ...
- 1,425
30
votes
7
answers
37k
views
`tail -f` until text is seen
I've got a CI server with a command-line interface that allows me to remotely kick-off a job (jenkins CI server and the jenkins-cli.jar tool).
After I kick the job off I tail -f the log (sorry for ...
- 504
39
votes
7
answers
35k
views
Read a line-oriented file which may not end with a newline
I have a file named /tmp/urlFile where each line represents a url. I am trying to read from the file as follows:
cat "/tmp/urlFile" | while read url
do
echo $url
done
If the last line doesn't end ...
- 107k
27
votes
3
answers
18k
views
Are files opened by processes loaded into RAM?
Commands, for instance sed, are programs and programs are codified logic inside a file and these files are somewhere on the hard disk. However when commands are being run, a copy of their files from ...
- 3,840
16
votes
6
answers
14k
views
If using while read loops for text processing in bash is bad...what should I do, then?
I guess this may be a naive question but I can't get my head around so I felt like asking...
I was searching for some solution to a problem, when I found this very interesting post about why is using [...
- 401
22
votes
2
answers
4k
views
Ask for a password in POSIX-compliant shell?
When I want to ask for a password in a bash script, I do that :
read -s
...but when I run bash in POSIX mode, with sh, the -s option is rejected:
$ read -s
sh: 1: read: Illegal option -s
How do I ...
- 691
6
votes
13
answers
2k
views
UNIX command to add comma and space
I have a file that looks like
$ cat IP
10.3.1.1
10.4.1.1
10.6.3.1
10.19.4.2
10.22.3.4
How do I make it look like:
$ cat IP
10.3.1.1, 10.4.1.1, 10.6.3.1, 10.19.4.2, 10.22.3.4
13
votes
7
answers
10k
views
How can I add random string for each line?
I'm trying to add random string for each line while running:
awk '{print "name" "'$ran'" "-"$0}' 'myfile'
Before that, the random string is generated:
ran="$(tr -dc '[:alnum:]' </dev/urandom | ...
- 273
7
votes
7
answers
25k
views
How to compare 2 strings in UNIX shell script? [duplicate]
I have a variable which stores a string, the output of a sed command.
I want to execute a set of commands only if this string value matches either of the 2 other strings.
I used the below code.
#! /...
- 145
17
votes
3
answers
11k
views
How to read different lines of a file to different variables?
I would like to read different lines of a text file to different variables. For example
input.txt:
line1 foo foobar bar
line2 bar
line3 foo
line4 foobar bar
I want this result to be stored in ...
- 179
15
votes
4
answers
4k
views
How to add new line between `ls -l` output
This is standard ls -l output.
user@linux:~$ ls -l
total 0
-rw-rw-r-- 1 user user 0 Nov 1 00:00 file01
-rw-rw-r-- 1 user user 0 Nov 1 00:00 file02
-rw-rw-r-- 1 user user 0 Nov 1 00:00 file03
...
user264359
10
votes
4
answers
2k
views
Performance of loop vs expansion
Need expert suggestions on below comparison:
Code Segment using loop:
for file in `cat large_file_list`
do
gzip -d $file
done
Code segment using simple expansion:
gzip -d `cat ...
- 259
9
votes
3
answers
49k
views
Find command - argument list too long
Oracle Linux 5.10
BASH shell
[oracle@src01]$ getconf ARG_MAX
131072
[oracle@srv01]$ ls -1 | wc -l
40496
#!/bin/bash
#
# delete files in /imr_report_repo that are older than 15-days
find /...
- 369