Using multiple patterns at once with Sed command

Here’s a question from one of our regular readers Mr. Manish.  His question is, how to use multiple patterns at once with the Sed command in Linux for delete or replace operations.

Consider an example file containing the following text. (I’m using the same example the reader asked for).

SLURM_CLUSTER_NAME = test
SLURM_JOB_ID = 525595
SLURM_JOB_NAME = test1
SLURM_JOB_USER = test
SLURM_JOB_NODELIST = cn01
SLURM_JOB_UID = 5016
SLURM_JOB_PARTITION = standard-low
SLURM_SUBMIT_DIR = /home/test
SLURM_TASK_PID = 108983
SLURM_CPUS_ON_NODE = 1
SLURM_NTASKS = 
SLURM_TASK_PID = 108983

Now the reader wants a single Sed command to delete the lines that match the pattern – SLURM_JOB_USER & SLURM_SUBMIT_DIR from the file. So how do you do that? Here we go.

Delete line matching pattern and print with Sed

Syntax:

$ set '/PATTERN/d' filename

$ sed '/SLURM_JOB_USER/d' test.txt

The above command will delete the line matching the pattern ‘SLURM_JOB_USER‘ and prints the output to the stdout.

Delete line matching pattern and modify the file with Sed

Syntax:

$ set -i '/PATTERN/d' filename

The '-i' option will modify the file.

$ sed -i '/SLURM_JOB_USER/d' test.txt

Using multiple patterns at once with Sed

What if you want to delete multiple lines matching multiple patterns with a single  Sed command? Here we go,

Syntax:

$ set -i '/PATTERN1/d;/PATTERN2/d' filename

$  sed -i '/SLURM_JOB_USER/d;/SLURM_SUBMIT_DIR/d' test.txt

The above command will delete the lines containing SLURM_JOB_USER and SLURM_SUBMIT_DIR patterns and save the file. Note the semicolon (;) for inputting multiple patterns within the single command.

Replace pattern and print out with Sed

Syntax:

$ sed 's/PATTERN/REPLACE_STRING/g' test.txt

$ sed 's/SLURM_JOB_USER/REPLACE1/g' test.txt

'g' represents global  – it replaces all instances of the pattern in each line, instead of just the first (which is the default behavior)

Replace pattern and modify the file with Sed

$ sed -i 's/SLURM_JOB_USER/REPLACE1/g' test.txt

Option '-i' will modify the file.

Use multiple patterns at once with Sed

$ sed -i 's/SLURM_JOB_USER/REPLACE1/g;s/SLURM_SUBMIT_DIR/REPLACE2/g' test.txt

Look out for the semicolon(;) to add more patterns within the single command.

Love it? Let us know if you have a query in the comments below and we will try covering it here.

Reference