---
name: "replacekey"
section: "1"
platform: "linux"
package: "qfits-tools"
version: "6.2.0-9+b1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/replacekey"
---

# replacekey(1)

replace keywords in a FITS header

## NAME

replacekey - replace keywords in a FITS header

## SYNOPSIS

**replacekey** \[options\] \<in\>

## DESCRIPTION

**replacekey** is aimed at replacing keywords in a FITS file's header by new keywords provided by the user on the command-line.

## ALGORITHM

The user can provide a new\_keyword, an old\_keyword, a value and a comment. **replacekey** first searchs for old\_keyword if provided. If it finds it, it replaces the associated card by the new one (new\_keyword=value/comment). If old\_keyword is either not found or not provided, **replacekey** searchs for new\_keyword, and if it finds it, replaces the associated card by the new one (new\_keyword=value/comment). new\_keyword has to be provided.

Examples: You want to change the value of VALUE from 32 to 16 in myfile.fits: % replacekey -k "VALUE" -v "16" myfile.fits

If you want to replace the card with the keyword OLD by  "NEW = 3.14 / This is a usefull key" in myfile.fits: % replacekey -k "NEW" -v "3.14" -c "This is a usefull key" -K "OLD" myfile.fits

If your do not care about the HISTORY cards you have in the header, and want to replace the first one by VALUE=32, you would do:\
 % replacekey -k "VALUE" -v "32" -K "HISTORY" myfile.fits

## OPTIONS

- **-k or --key key**

  To provide the new keyword.

- **-K or --old key**

  To provide the old keyword.

- **-v or --val val**

  To provide the new value.

- **-c or --com com**

  To provide the new comment.

## SEE ALSO

**hierarch28** to convert HIERARCH ESO keywords to regular 8-char keywords.

## FILES

Files shall all comply with FITS format

## BUGS

Modifications are so far only possible in the main header, not in the extensions.