Error when storing the first line of a file to a variable

Question

I am doing basic programs with Linux shell scripting(bash)

I want to read the first line of a file and store it in a variable .

My input file :

100|Surender|CHN
101|Raja|BNG
102|Kumar|CHN

My shell script is below

first_line=cat /home/user/inputfiles/records.txt | head -1
echo $first_line

I am executing the shell script with bash records.sh

It throws me error as

 /home/user/inputfiles/records.txt line 1: command not found

Could some one help me on this

vitaut · Accepted Answer · 2015-12-12T15:24:19.077

1

The line

first_line=cat /home/user/inputfiles/records.txt | head -1

sets variable first_line to cat and then tries to execute the rest as a command resulting in an error.

You should use command substitution to execute cat .../records.txt | head -1 as a command:

first_line=`cat /home/user/inputfiles/records.txt | head -1`
echo $first_line

edited Dec 12 '15 at 15:24

answered Dec 12 '15 at 15:22

vitaut

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Thanks, I tried as Per your suggestion and it worked . Could you also tell me when do I need to go and apply backticks while writing shell script – Surender Raja Dec 12 '15 at 15:24
You need to use backticks (command substitution) whenever you want to use the output of some command to replace the command itself. – vitaut Dec 12 '15 at 15:27
Ok fine. Thanks again – Surender Raja Dec 12 '15 at 15:30

score 1 · Answer 2 · answered Dec 12 '15 at 18:00

The other answer addresses the obvious mistake you made. Though, you're not using the idiomatic way of reading the first line of a file. Please consider this instead (more efficient, avoiding a subshell, a pipe, two external processes among which a useless use of cat):

IFS= read -r first_line < /home/user/inputfiles/records.txt

Error when storing the first line of a file to a variable

2 Answers2