This is a basic introduction to the edify scripting language used by Android to run updater-scripts. Before I begin, I learned pretty much everything I know about edify scripting from E. Pete Karelis; so huge credit goes out to him for the contents of this guide.
Lesson number one: Pretty much all of the commands in Edify are functions; they return data to the script when the function call is complete. You can, of course, use the function's return value to establish success or failure, like so:
ifelse(mount("yaffs2", "MTD", "system", "/system") == "system", ui_print("Successfully Mounted!"), ui_print("Mount Failed!");
This command will attempt to mount the MTD partition named "system" to "/system". If the mount succeeds, the script will display Successfully Mounted!, otherwise(else) it will display Mount Failed!
Below are examples of functions used in an Edify Updater-script:
Function Name: mount
Function Syntax: mount(fs_type, partition_type, location, mount_point)
Parameter Details:
fs_type = "yaffs2" | "ext4"
partition_type="MTD" | "EMMC"
location = partition | device
mount_point = target folder to mount FS.
Action: Mounts a filesystem to the defined mount point
Returns: The mount point if successful, null if failed
Function Name: is_mounted
Function Syntax: is_mounted(mount_point)
Parameter Details: mount_point = string, mount point to check if is mounted
Action: Checks if a filesystem is mounted.
Returns: The mount point if mounted, otherwise, returns null
Function Name: unmount
Function Syntax: unmount(mount_point)
Parameter Details: mount_point = string, mount point to unmount
Action: Unmounts the filesystem
Returns: The mount point that was dismounted if successful, otherwise it returns null
Function Name: format
Function Syntax: format(fs_type, partition_type, location)
Parameter Details:
fs_type = string,"yaffs2" | "ext4"
partition_type= string, "MTD" | "EMMC"
location = string, partition | device
Action: Formats a filesystem as specified
Function Name: delete
Function Syntax: delete(file1, file2, ..., fileN)
Parameter Details: string, file to delete
Action: Deletes a file. Must specify at least one file; multiple files can be specified as multiple arguments
Function Name: delete_recursive
Function Syntax: delete_recursive(dir1, dir2,...,dirN)
Parameter Details: string, directory to recursively delete
Action: Deletes a folder and all of its contents. At least 1 directory must be specified; multiple directories can be specified as additional arguments.
Function Name: show_progress
Function Syntax: show_progress(frac, sec)
Parameter Details:
frac = fraction of progress completed
sec = total seconds
Action: Displays flashing progress in the recovery system
Function Name: set_progress
Function Syntax: set_prograss(frac)
Parameter Details: frac=fraction of progress
Function Name: package_extract_dir
Function Syntax: package_extract_dir(package_path, destination_path)
Parameter Details:
package_path = string, directory in package to extract
destination_path = string, target point to extract files to
Action: Extract the all of the files in a directory in the package to the target specified.
Function Name: package_extract_file
Function Syntax:
package_extract_file(package_path)
or
package_extract_file(package_path, destination_path)
Parameter Details:
package_path = string, file in the package you want to extract
destination_path, target folder to extract the file to.
Action: Extracts a single file from your update package to the target specified
Function Name: file_getprop
Function Syntax: file_getprop(file, key)
Parameter Details:
file = string, filename to check
key = string, key in file to return the value of
Action: Checks for a value in a file?
Function Name: symlink
Function Syntax: symlink(target, src1, src2, ..., srcN)
Parameter Details:
target = string, the target of the symbolic link
srcX = the symbolic link to create that points to the target
Action: Unlinks any existing symbolic links before creating the new symbolic links.
Function Name: set_perm
Function Syntax: set_perm(uid, gid, mode, file1, file2, ..., fileN)
Parameter Details:
uid = user id
gid = group id
mode = permission mode
fileX = file to set permission on
Action: Sets permissions of a file or set of files specified. At least one file must be specified (the first four parameters are required)
Function Name: set_perm_recursive
Function Syntax: set_perm_recursive(uid, gid, dirmode, filemode, dir1, dir2, ...dirN)
Parameter Details:
uid = user id
gid = group id
dirmode = permission to set to directories contained within the specified directory
filemode = permission to set to files contained within the specified directory
dirX = directory to set permission on
Action: Set permissions of a directory or set of directories and all files and folders within them. At least one directory must be specified (The first 5 parameters are required)
Function Name: getprop
Function Syntax: getprop(key)
Parameter Details: key = string, the property you want the system to return
Action: This function returns the value of the property specified. This is used to query platform information from the build.props file.
Function Name: write_raw_image
Function Syntax: write_raw_image(file, partition)
Parameter Details:
file - string, the source .img file to be read from
partition - string, the destination partition to write the .img file to
Description: This function writes an img file to a partition.
Function Name: apply_patch
Function Syntax: apply_patch(srcfile, tgtfile, tgtsha1, tgtsize, sha1_1, patch_1, ..., sha1_x, patch1_x)
Parameter Details:
srcfile - string, source file to be patched (file to read in)
tgtfile - string, destination file to write the patched file to
tgtsha1 - string, sha1 hash of the target file as it should hash out after the patches apply properly
sha1_x - string, sha1 hash of the patch data that's to be written to the target file
patch1_x- string, actual patch to apply to the target file
Action: This function is used to apply patches to a file.
Function Name: apply_patch_check
Function Syntax: apply_patch_check(file, sha1_1, ..., sha1_x)
Parameter Details:
file - string, file to check
sha1_x - hash to check for?
Action: Either checks if a file has been properly patched, or checks if a file can be patched. Need to check the source code of the "applypatch_check" function that is called from here.
Function Name: apply_patch_space
Function Syntax: apply_patch_space(bytes)
Parameter Details: bytes = number of bytes to check for
Action: Checks the cache to verify that there is enough space to write the patched files to it and returns something. Need to test this function to verify.
Function Name: read_file
Function Syntax: read_file(filename)
Parameter Details: filename - string, the filename to read the contents of
Action: This function returns the contents of a file.
Function Name: sha1_check
Function Syntax:
sha1_check(data)
or
sha1_check(data, sha1_hex, ..., sha1_hexN)
Parameter Details:
data - the contents of file to calculate the sha1 hash of - must be in the read_file format
sha1_hexN - A particular sha1_hex string that you want the file data to match
Action: If only data is specified, then the function returns the sha1_hex string of the data. The optional parameters are used if you want to verify that the file you are checking for is one of a list of hashes. It reutrns the hash it matches, or returns nothing if it doesn't match any of the mentioned hashses.
Function Name: ui_print
Function Syntax: ui_print(msg1, ..., msgN)
Parameter Details: msg - String, message to be outputted to the user during the patch process
Action: This function prints/echos a message to the console while the script is running. At least 1 parameter needs to be specified, you can specify additional msg parameters and they will be concatenated to the output.
Function Name: run_program
Function Syntax: run_program(prog, arg1, .., argN)
Parameter Details:
prog - string, program to execute
argN - string, arguments for the program that is being executed
Description: Executes a program with the arguments specified. Returns a string, I assume it is the buffer of the stdout of the program executed, need to test.
Function Name: ifelse
Function Syntax: ifelse(condition, truecondition, falsecondition)
Parameter Details:
condition - an expression to evaluate
truecondition - Edify script block to execute if true
falsecodnition - Edify script block to execute if false
Description: This is the if-then construct of the Edify scripting language. The truecondition or falsecondition arguments can be a single edify command or a script block. Script blocks can be formed by enclosing the parameter with parenthesis, and seperating the commands with semicolons\
Function Name: abort
Function Syntax: abort()
Parameter Details: no paremeters
Description: Aborts script execution.
Function Name: assert
Function Syntax: assert(condition)
Parameter Details: condition - boolean
Description: If condition evaluates to false, stops script execution, otherwise continues processing.
There are more functions than have been mentioned above, and I will continue to update this list as and when possible!