This is workflow for downloading, processing, and mosaicing Landsat scenes, as a Makefile

Makefile

# lansatutil directory
LANDSAT = ~/landsat

# scenes to target
LANDSAT_IDS = \
	LC81220442016038LGN00 \
	LC81220452016038LGN00 \
	LC81210442014281LGN00 \
	LC81210452014281LGN00

# where to put processed files
LOCAL_PROCESSED = ./processed

# Define projection for the output
PROJECTION = +proj=utm +zone=50 +datum=WGS84

# if you run `make` create a stitched auto contrasted mosaic using bands 4, 3, and 2 for the specified IDs 
all:: $(LOCAL_PROCESSED)/stiched_autocontrast_432.tiff

# create a function to use while iterating over the IDs
# the variable $1 is always the current ID
define landsat-workflow

download_all:: $(LANDSAT)/downloads/$1/$1_MTL.txt
	
$(LANDSAT)/downloads/$1/$1_MTL.txt:
	# download bands 4, 3, 2, and 8 of the specified ID
	landsat download $1 --bands 4328

process432:: $(LOCAL_PROCESSED)/$1_rgb.tif

$(LOCAL_PROCESSED)/$1_rgb.tif: ~/landsat/downloads/$1/$1_MTL.txt $(LOCAL_PROCESSED)
	# create a 432 composite of the specified IDs bands
	# $$@ is the target for the rule i.e. $(LOCAL_PROCESSED)/$1_rgb.tif
	gdal_merge.py \
		-co "PHOTOMETRIC=RGB" \
		-separate ~/landsat/downloads/$1/$1_B{4,3,2}.TIF \
		-o $$@

warptoutm50:: $(LOCAL_PROCESSED)/$1_rgb_resized_utm50.tif

$(LOCAL_PROCESSED)/$1_rgb_resized_utm50.tif: $(LOCAL_PROCESSED)/$1_rgb.tif
	# remove an existing file of the target name because gdal will fail if it's there
	rm -f $(LOCAL_PROCESSED)/$1_rgb_resized_utm50.tif
	
	# reproject the specifed scene to UTM 50 and resize to to be 1000px wide using cubic sampling
	# $$< are the required files for the rule $$@ is the target for the rule
	gdalwarp \
		-co "PHOTOMETRIC=RGB" \
		-t_srs '$(PROJECTION)' \
		-ts 1000 0 \
		-r cubic \
		$$< \
		$$@
		
# if you run `make` create all the resized reprojected scenes
all:: $(LOCAL_PROCESSED)/$1_rgb_resized_utm50.tif

endef

stich_432: $(LOCAL_PROCESSED)/stiched_432.tiff
	
$(LOCAL_PROCESSED)/stiched_432.tiff: $(addprefix $(LOCAL_PROCESSED)/,$(addsuffix _rgb_resized_utm50.tif, $(LANDSAT_IDS))) 
	# stitch together the resized reprojected scenes into one mosaic
	# $@ is the target for the rule $^ are the requirements
	schooner-stitch \
		$^ \
		$@

autocontrast432: $(LOCAL_PROCESSED)/stiched_contrast_432.tiff

$(LOCAL_PROCESSED)/stiched_autocontrast_432.tiff: $(LOCAL_PROCESSED)/stiched_432.tiff
	# create a new version of the mosaic with enhanced contrast
	schooner-contrast $(LOCAL_PROCESSED)/stiched_432.tiff $(LOCAL_PROCESSED)/stiched_autocontrast_432.tiff

$(LOCAL_PROCESSED):
	#make sure you have your folder to hold processed images
	mkdir $@

# iterate over the IDs passing each into the landsat-workflow function to create the rules it contains contained
$(foreach 1, $(LANDSAT_IDS),$(eval $(call landsat-workflow,$1)))