Convert Multiple Rows into Single Row in Linux

In this article, we are going to see how to convert multiple rows into a single row using Linux.

Here is the file for demonstration:

Method 1: Using Pure Bash

Let us convert multiple rows into a single row using pure bash since it is the default shell, please make a note that bash shell does not depend on other utilities as it makes use of only built-in commands :

We use the above input file as a template to perform our desired operation i.e converting multiple rows into a single row in Linux.

Syntax: $ (readarray -t ARRAY < inputfile.txt; IFS=”; echo “${ARRAY[*]}”)

Where:

• The readarray is a Bash built-in command. It was introduced in Bash ver.4. The readarray is used for reading inputs standard input into an array variable: ARRAY.
• The -t option is handy for removing
• The IFS is a special shell variable which ia an abbreviation for Internal Field Separator. Here, we assigned the IFS with a single character, empty or ‘,’ depends on our requirements.
• ${ARRAY[*]} means all elements surrounded in ARRAY variable, by using the  echo command, all elements of ARRAY will be printed out which are separated  by the IFS variables.

Example:

$ (readarray -t ARRAY < newfile.txt; IFS=''; echo "${ARRAY[*]}")

Output :

Method 2: Using tr command

tr is a command which is handy at deletion and translation of specific characters fetched from the standard input file.

Syntax: $ tr [OPTION] SET1 [SET2]

The tr command can simply do this job by simply by removing line breaks from the file content.

Example:

$ tr -d '\n' ',' <newfile.txt

Output :

Method 3: Using Paste command

Paste command is handy for joining files horizontally by outputting lines consisting of lines from each file specified.

Syntax : paste [OPTION]… [FILES]…

The paste command is used for merging lines belonging to multiple input files. This Merging operation by default is executed in such a way  that entries in the first column belong to the first file, and the ones in the second column are for the second file.The -s option can let it merge lines row-wise.

Example:

$ paste -sd ',' newfile.txt 

Output : 

Method 4: Using sed command

Sed in Unix is an abbreviation for stream editor, which is handy in executing different kinds of operations like searching, find and replace, insertion or deletion. 

Syntax : sed OPTIONS… [SCRIPT] [INPUTFILE…] 

Here, the motto of using sed one-liner is: append each line into the pattern space, at last replace all line breaks with the given string. 

Example:

$ sed ':a; N; $!ba; s/\n/,/g'  newfile.txt

Output :