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* Move commands from docs to its own root-level directory * temporarily use modified dev-portal branch with nomad ia changes * explicitly clone nomad ia exp branch * retrigger build, fixed dev-portal broken build * architecture, concepts and get started individual pages * fix get started section destinations * reference section * update repo comment in website-build.sh to show branch * docs nav file update capitalization * update capitalization to force deploy * remove nomad-vs-kubernetes dir; move content to what is nomad pg * job section * Nomad operations category, deploy section * operations category, govern section * operations - manage * operations/scale; concepts scheduling fix * networking * monitor * secure section * remote auth-methods folder and move up pages to sso; linkcheck * Fix install2deploy redirects * fix architecture redirects * Job section: Add missing section index pages * Add section index pages so breadcrumbs build correctly * concepts/index fix front matter indentation * move task driver plugin config to new deploy section * Finish adding full URL to tutorials links in nav * change SSO to Authentication in nav and file system * Docs NomadIA: Move tutorials into NomadIA branch (#26132) * Move governance and policy from tutorials to docs * Move tutorials content to job-declare section * run jobs section * stateful workloads * advanced job scheduling * deploy section * manage section * monitor section * secure/acl and secure/authorization * fix example that contains an unseal key in real format * remove images from sso-vault * secure/traffic * secure/workload-identities * vault-acl change unseal key and root token in command output sample * remove lines from sample output * fix front matter * move nomad pack tutorials to tools * search/replace /nomad/tutorials links * update acl overview with content from deleted architecture/acl * fix spelling mistake * linkcheck - fix broken links * fix link to Nomad variables tutorial * fix link to Prometheus tutorial * move who uses Nomad to use cases page; move spec/config shortcuts add dividers * Move Consul out of Integrations; move namespaces to govern * move integrations/vault to secure/vault; delete integrations * move ref arch to docs; rename Deploy Nomad back to Install Nomad * address feedback * linkcheck fixes * Fixed raw_exec redirect * add info from /nomad/tutorials/manage-jobs/jobs * update page content with newer tutorial * link updates for architecture sub-folders * Add redirects for removed section index pages. Fix links. * fix broken links from linkcheck * Revert to use dev-portal main branch instead of nomadIA branch * build workaround: add intro-nav-data.json with single entry * fix content-check error * add intro directory to get around Vercel build error * workound for emtpry directory * remove mdx from /intro/ to fix content-check and git snafu * Add intro index.mdx so Vercel build should work --------- Co-authored-by: Tu Nguyen <im2nguyen@gmail.com>
59 lines
2.0 KiB
Plaintext
59 lines
2.0 KiB
Plaintext
---
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layout: docs
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page_title: can - Functions - Configuration Language
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description: |-
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The can function tries to evaluate an expression given as an argument and
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indicates whether the evaluation succeeded.
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---
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# `can` Function
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`can` evaluates the given expression and returns a boolean value indicating
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whether the expression produced a result without any errors.
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This is a special function that is able to catch errors produced when evaluating
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its argument. For most situations where you could use `can` it's better to use
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[`try`](/nomad/docs/reference/hcl2/functions/conversion/try) instead, because it allows for more concise definition of
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fallback values for failing expressions.
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The `can` function can only catch and handle _dynamic_ errors resulting from
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access to data that isn't known until runtime. It will not catch errors
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relating to expressions that can be proven to be invalid for any input, such
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as a malformed reference.
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~> **Warning:** The `can` function is intended only for simple tests in
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variable validation rules. Although it can technically accept any sort of
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expression and be used elsewhere in the configuration, we recommend against
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using it in other contexts. For error handling elsewhere in the configuration,
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prefer to use [`try`](/nomad/docs/reference/hcl2/functions/conversion/try).
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## Examples
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```shell-session
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> local.foo
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{
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"bar" = "baz"
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}
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> can(local.foo.bar)
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true
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> can(local.foo.boop)
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false
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```
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The `can` function will _not_ catch errors relating to constructs that are
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provably invalid even before dynamic expression evaluation, such as a malformed
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reference or a reference to a top-level object that has not been declared:
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```shell-session
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> can(local.nonexist)
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Error: Reference to undeclared local value
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A local value with the name "nonexist" has not been declared.
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```
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## Related Functions
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- [`try`](/nomad/docs/reference/hcl2/functions/conversion/try), which tries evaluating a sequence of expressions and
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returns the result of the first one that succeeds.
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