The variable tag has no wiki summary.
1
vote
2answers
99 views
Execution of a command in a variable with eval
I am trying to use grep to color some log files . I wrote a script and a part of it looks like this :
#!/bin/bash
com="GREP_COLOR=\"1;36\" egrep --color=always '[^a-zA-Z0-9]' $log |less -R"
...
0
votes
5answers
63 views
How can I modify variables
I have the following variable:
col=1,3,4,
Is there anyway to select the numbers within the variable: (i.e. 1 3 4 and work with them?
Such as choosing the "1", "3", or "4" column from a .txt file?
...
1
vote
1answer
59 views
prevent bash completion from altering underscore variable $_
When using tab completion in bash, the $_ variable is altered:
$ mkdir test
$ cd <TAB><TAB> $_
bash: cd: -d: invalid option
cd: usage: cd [-L|[-P [-e]]] [dir]
(The ...
1
vote
4answers
98 views
Reusing a variable
I was breaking my head for a day still not successful.
I have this script:
#!/bin/ksh
fname=$1
for batchname in $(grep -i "Processing batch" $fname | cut -d "'" -f2)
do
Batch_state=`grep -c -i ...
0
votes
2answers
59 views
Why must you be careful when using Bash's built in command history function to re-run previous commands that contain variables?
I know !! re-runs commands but what exactly would occur if I re-ran a command that had a variable in the command?
0
votes
1answer
50 views
LD_LIBRARY_PATH not found - CentOS
I am trying to run the following two commands...
LD_LIBRARY_PATH =/opt/oracle/instantclient_12_1
export
LD_LIBRARY_PATH
But when I run the first command I get an error
-bash: ...
1
vote
2answers
110 views
how can I add (subtract, etc.) two numbers with bash?
I can read the numbers and operation in with:
echo "First number please"
read num1
echo "Second mumber please"
read num2
echo "Operation?"
read op
but then all my attempts to add the numbers fail:
...
1
vote
2answers
40 views
awk,how to change the value of the file using parameter sets?
I am trying to reset my data using awk.
I have a data of 54 columns where I want to change six of the column values using the following script.
#!/bin/bash -x
# optimal parameters
set ...
2
votes
2answers
68 views
Creating temp file vs process substituion vs variable expansion?
If I am doing something like
creating temporary file
some process generating output > temp_file
cat temp_file
process substitution:
cat <(some process generating output)
another way :
...
2
votes
4answers
82 views
Scope of variables when calling function from find
In a bash script I define a function that is called from find. The problem is that the scope of variables does not extend to the function. How do I access variables from the function? Here is an ...
2
votes
1answer
31 views
How to take advantage of gnuplot internal functions by column reference at shell
I want to do something like:
echo "p 'myfile.txt' u 1:(exp($2))" | gnuplot -p
but need the shell to pass the $2 as a literal into gnuplot.
2
votes
4answers
130 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 $5}' ...
2
votes
4answers
131 views
Setting a variable whose value depends on another variable
i have a text file variables.txt where i store my variables
host=/srv/www/vhosts/hosting
index=$host/index.php
as you see the second variables depends on the first one.
i also have a ...
2
votes
1answer
87 views
prevent trap from altering underscore variable $_
I have the following code in my bashrc to get the execution time of the last command from http://stackoverflow.com/a/1862762
function timer_start {
timer=${timer:-$SECONDS}
}
function timer_stop {
...
40
votes
2answers
2k views
What NOT to put on an SSD?
I bought an SSD and I am going to set up my desktop system with a completely fresh Linux installation.
SSDs are known to be fast, but they have a disadvantage: The number of writes (per block?) is ...
1
vote
2answers
39 views
Associating variable with specific for loop file
I want to use for for a set of files.
for file in fileA fileB fileC; do
COMMAND $file $variable
done
For every $file I want to use specific $variable.
(for example: fileA variableA; fileB ...
1
vote
2answers
99 views
for loop to get more than one arguments
In python and some other programming languages, it is easy to get a vector instead of one variable everywhere and in loops. like python:
for variable in ...
0
votes
1answer
66 views
How can I use a variable from a script?
A bash script is running as I defined it in Startup Applications. It is possible to display on terminal a variable used in that script? If yes, how?
2
votes
1answer
97 views
What does “${x%% *}” mean in sh? [duplicate]
I just saw "$${x%% *}" in a makefile, which means "${x%% *}" in sh.
Why it is written in this way ?
how can a makefile detect whether a command is available in the local machine?
determine_sum = \
...
0
votes
2answers
669 views
bash - reading user variable into bash script grep
I've tried every possible combination to get this bash script working. It's part of a larger script, and it basically prompts for a username (to check if it exists) and returns the appropriate ...
2
votes
2answers
66 views
List all my variables [duplicate]
I'm just learning the basics, including how to declare and mess around with variables. Is there a simple way to display a list of all the variables I've named? (Everything I've found by searching only ...
0
votes
1answer
151 views
How can I preserve new lines coming from a command's output during variable assignment?
Consider:
$ getfacl somefile.dat # The output is formatted and contains several new lines..
# file: somefile.dat
# owner: user1
# group: group1
user::rw-
group::r-- #effective:r--
...
1
vote
2answers
108 views
How to print shell variables and values to be able to copy/paste them?
In Bash 4.2.25, the set and env output is not escaped, so shell escapes and any non-printable characters won't be copy-pasteable. Take for example this shell session:
$ export foo=$'a\nbar=\baz'
$ ...
1
vote
1answer
137 views
What does mean ` AWK=@AWK@` in shell scripting
I found AWK=@AWK@ while reading sh script, it's something like AWK=$(which awk), but it's not working.
So can anyone explain this ?
Script :
#!/bin/sh -
# makelist.sh: Automatically generate header ...
1
vote
2answers
238 views
How do I set bash aliases and variables from within vim?
In cmdline mode, the following examples do not work for me.
!alias lol='echo lol'
!lol='echo lol'
2
votes
1answer
212 views
shell variable in awk is not being passed to all the lines but just for the very first line of input?
inputfile:is2.txt
10.39.5.41,A1,B1
10.39.5.41,A2,B2
10.39.5.41,A3,B3
10.39.5.41,A4,B4
10.39.5.41,A5,B5
10.39.5.41,A6,B6
script :
#!/bin/bash
second_column="OOOOOOO" # OOOOOOO will be added to ...
3
votes
2answers
122 views
Setting a shell variable in a null coalescing fashion
I'm really fond of "null coalescing", where you can set a variable to the first "non-null" value in a list of things. Many languages support this, for example:
C#:
String myStr = string1 ?? string2 ...
