This page explains how to configure Cloud Build to run bash scripts within a build step. If you're new to Cloud Build, read the quickstarts and the Build configuration overview first.
You can run bash scripts within a build step to configure a number of workflows including:
- Running multiple commands in one build step.
- Reading from the filesystem.
- Building in logic such as retries or conditionals.
- Outputting to the log, for example, running
echo $VARNAME
.
To run bash scripts in a build step, you can either use the
bash
image,
or any other image that has bash
installed in it. Standard base images such as
ubuntu
and debian
can run bash scripts. Some of the
supported cloud builders
such as the gcloud
and the docker
builders also have bash
installed in them.
To find out if an image has bash installed in it, check the image's Dockerfile.
Running inline bash scripts
To run bash commands using the bash
image, specify bash
as the name
of the build step, and the command in the args field:
YAML
steps:
- name: 'bash'
args: ['echo', 'I am running a bash command']
JSON
{
"steps": [
{
"name": "bash",
"args": [
"echo",
"I am running a bash command"
]
}
]
}
If the image you're using comes prepackaged with bash
but if bash
is not the
default entrypoint, add an entrypoint
field pointing to bash
. In the example
below, the bash
entrypoint is used to run gcloud
commands that query
Cloud Build for build status, listing builds with a failed status.
YAML
steps:
- name: 'gcr.io/google.com/cloudsdktool/cloud-sdk'
entrypoint: 'bash'
args:
- '-eEuo'
- 'pipefail'
- '-c'
- |-
gcloud builds list > builds.txt
while read line; do
if grep -q "FAILURE" <<< "$line"; then
echo "$line"
fi
done < builds.txt
JSON
{
"steps": [
{
"name": "gcr.io/google.com/cloudsdktool/cloud-sdk",
"entrypoint": "bash",
"args": [
"-eEuo",
"pipefail",
"-c",
"gcloud builds list > builds.txt\nwhile read line; do\n if grep -q \"FAILURE\" <<< \"$line\"; then\n echo \"$line\"\n fi\ndone < builds.txt"
]
}
]
}
The -c
flag in the code above is used to execute multi-line commands. Any string
you pass after -c
is treated as a command. For more information on running bash
commands with -c
, see the
bash documentation.
Running bash scripts on disk
If you have your bash script saved in a file, store the file along with your build source, and reference the script file within your build config file:
YAML
steps:
- name: 'bash'
args: ['./myscript.bash']
JSON
{
"steps": [
{
"name": "bash",
"args": [
"./myscript.bash"
]
}
]
}
To use a bash script on file if bash is not the default entrypoint of the image
you're using, add an entrypoint
field pointing to bash:
YAML
steps:
- name: 'gcr.io/cloud-builders/gcloud'
entrypoint: 'bash'
args: ['tools/myScript.sh','--foo']
JSON
{
"steps": [
{
"name": "gcr.io/cloud-builders/gcloud",
"entrypoint": "bash",
"args": [
"tools/myScript.sh",
"--foo"
]
}
]
}
Using the script
field
Cloud Build provides a script
field that you can use to specify
shell scripts to execute in a build step. The script
field takes a single string
value. You can prefix the string with a shebang to specify the shell to interpret the script. If you don't
prefix the script string with a shebang, Cloud Build uses #!/bin/sh
(i.e., the basic sh shell, not Bash).
If you specify script
in a build step, you cannot specify args
or entrypoint
in the same step.
The following snippet demonstrates the script
field:
YAML
steps:
- name: ubuntu
script: echo hello
- name: python
script: |
#!/usr/bin/env python
print('hello from python')
JSON
{
"steps": [
{
"name": "ubuntu",
"script": "echo hello"
},
{
"name": "python",
"script": "print('hello from python')\n"
}
]
}
What's next
- Learn how to start a build manually.
- Learn how to automate builds using triggers.
- Learn how to configure build step order.
- Learn how to use community-contributed builders and custom builders.